Planet of the Dead (TV story)

Planet of the Dead is the title of the first of the 2009 specials, which first aired on 11 April 2009. It starred David Tennant and featured two new characters, Christina and Malcolm, along with UNIT. Production of the special began on 19th January 2009.

It was broadcast for Easter, on Holy Saturday at 6.45PM. The BBC did not officially announce the broadcast date for the special until the beginning of April 2009.

Synopsis
The Doctor, along with The Lady Christina de Souza and other passengers, finds himself transported to a barren desert planet on a double-decker bus. As the Doctor and Christina struggle to uncover the mysteries beneath the sand, the Swarm draws closer.

Plot
Guards are protecting a golden cup inside a museum, later to be identified as the Cup of Athelstan, worth 18 million pounds. Lady Christina de Souza then lowers herself from the roof, and replaces the cup with a mechanical Japanese lucky cat; when the guards finally turn around at the sound of her releasing her winch on the roof, she waves at them in a mocking fashion. As the alarms go off, she runs out to the street to see someone being arrested, and she says, "Sorry, lover" to her presumed accomplice.

She then takes a back route onto the main road, where she frantically looks for a way out as police move in searching for her, although unaware of her presence. She runs onto a 200 bus to Victoria, where she exchanges her diamond earrings for a bus ride. Soon afterwards, a man wearing trainers, whose face we aren't shown, comes onto the bus, and uses a psychic paper on the Oyster Card scanner. He then sits down opposite Lady Christina, and is shown to be The Doctor. After enjoying a chocolate Easter egg and engaging in some small talk with Christina, he receives an alert from the rhondium sensor in his pocket that the particles he's been looking for have been detected.

The police are still after Christina, since they know she has stolen the Cup of Athelstan, but whilst chasing the bus through a tunnel, the police witness it disappear in front of their eyes; startled, they set up a perimeter around the area. Meanwhile, the bus passes through a warp into a world covered in desert: the planet San Helios, apparently completely deserted. The bus is wrecked in the process. By the time it arrives at the planet the driver proclaims it unmovable.

The Doctor tells the passengers that the bus has passed through a wormhole into a different world, proving this to them by throwing a handful of sand into the space behind the bus. The sand causes a rippling effect in the air. The Doctor says that the other end of the wormhole was in the tunnel on Earth. Among the passengers is Carmen, who has been hearing mysterious voices since Christina got on. The bus driver announces his desire to return to Earth, and promptly runs through the wormhole, accompanied by The Doctor's "No, don't!". The other passengers of the bus witness the driver's skin and tissues incinerating, before he disappears into the wormhole with the same rippling effect as the sand.

Meanwhile on Earth, where the police are watching the wormhole, the driver's blackened skeleton steps out, halts, and then tumbles to the ground. Unnerved, the police declare an emergency Code One, calling UNIT to the scene. Captain Erisa Magambo commands the operation and she tells her soldiers to fire at anything that comes through the wormhole.

Meanwhile, The Doctor explains to the passengers of the bus that the metal of the bus had protected them from the same fate as the driver (like a Faraday cage, as Christina states). The Doctor then attempts to call someone on Earth and gets in touch with UNIT at the tunnel. Speaking to Captain Magambo, the Doctor informs her of the crisis and speaks to UNIT's scientific advisor, Malcolm Taylor. They all set to digging the bus wheels out from the sand to try and enable them to move it back through the wormhole. The Doctor and Christina set off to explore the area, and find that there is what looks like a massive sandstorm sweeping across the planet towards them, glinting in the sun as if made from metal. They are then found and captured by a fly-like alien (later identified as a Tritovore).

The Doctor and Cristina are escorted to the Tritovore's crashed ship, where the Tritovore blame the Doctor for their crashed ship. The Doctor soon explains to the two Tritovores that they mean them no harm, and are trapped on the planet just as they are. The Tritovores in turn tell them their ship has crashed on the surface of the planet where they wanted to trade with the people of the world. The Doctor, though, claims that the entire planet became a desert last year, with all 100 billion inhabitants. The Doctor then asks them to send a probe out to invesigate the sandstorm seen earlier. It sends back results, showing that the storm is a swarm of billions of carnivorous stingray-like aliens with metal exoskeletons, before the transmission is cut off by the probe being eaten by one of the alien stingrays. The Doctor then analyzes the alien physique by the data they get and theorizes that they must be creating the wormhole effect, by their velocity and physiology buildup, and are immune to the effects of the Wormhole because their exoskeletons are metal.

The Tritovores and the Doctor plan to get away from the planet before the swarm hits their area, and need to get the crystal power source that makes the Tritovorian ship fly. The Doctor and the two aliens try to bring up the source manually, but the entire system is nonresponsive, lacking power. Christina, in the meantime, prepares her cat burgling equipment, and lines down the shaft. The Doctor stops her just in time before she is electrocuted by a security grid. After disabling it, she makes her way slowly down the shaft. The Doctor tells her about himself, and some of the places he's been, including the Court of Athelstan: but he didn't remember her being there, pulling the Cup of Athelstan out of her bag...

He realises that she's a thief, and she says she prefers to say she liberates things. While getting the crystal and the brackets she sees a stingray waking behind some metal poles, and the Doctor tells her that it is detecting her body heat and waking up. She replies she has that effect on men, and the Doctor brings her back up, saying that many must have flown into the ship's mainframe, and that is what crashed it, he says, like birds into a jet engine. The alien stingray which was down in the shaft next to Christina gives chase, getting fried in the security grid as she turns it back on on the way up. As they run away with the Tritovores out of the ship another stingray jumps down from above and kills one of the Tritovores, the other, in rage, prepares to fire its weapon at the Stingray but before he can is eaten as well.

The Doctor and Christina run to the bus, and after throwing away the crystal itself, the Doctor attaches 4 Tritovorian gravity grips onto the wheels, and uses the 5th to interface the bus steering wheel with the Tritovorian technology. However, it doesn't work, as the two technologies are incompatible alone; he needs something soft, malleable, non corrosive and able to conduct electricity, suggesting gold, to act as an interface. After she hands the Doctor the Cup of Athelstan, a hammer upon request, and the request to "be careful with it", he smashes it to bits so it fits between the bus wheel and the anti-gravity clamp controller. In response, Christina says "I hate you". The bus then lifts out of the sand and into the air, flying back through the wormhole to Earth. Once through, Christina passionately kisses the Doctor, reprising her earlier "hate".

As the bus flies across London, three stingrays chase them through the wormhole. UNIT soldiers shoot them down after a small battle. The bus lands back on the spot where it vanished, and the passengers are released and taken to be examined by UNIT. The Doctor meets Malcolm, who has closed the wormhole and in a frenzy of excitement, says "I love you!" four times to the Doctor. Magambo then reveals to the Doctor that they found the TARDIS at Buckingham Palace, revealing it in the back of a military truck. The Doctor recommends Nathan and Barclay for jobs at UNIT. Christina, meanwhile, is being searched by UNIT soldiers but she breaks off and runs to the Doctor. She wants to come with him for adventure and excitement, telling him that is why she steals, but he says no. When she asks him why, he tells her that he lost all his companions, and that he does not want that happening again. The police promptly arrest Christina, and take her away, leaving the unperturbed Doctor by himself.

The Doctor, about to enter the TARDIS, is told by Carmen to take care of himself; the Doctor, full of joy, tells her the same. However, she tells him "[Your song is ending, it is returning through the dark, and... he will knock four times."

Meanwhile, the Doctor decides to take pity on Christina, who is now handcuffed and being put in a police car. The Doctor points his sonic screwdriver at her handcuffs, and frees her hands. Christina gets in the police car on one side- and gets out on the other. She heads for the bus chased by the poice and closes the doors. The police inspector orders her to open them, but the Doctor advises him to step back. The inspector charges him with aiding and abetting; the Doctor heads over to the TARDIS, saying he will 'arrest himself'. The bus takes off, flies over the inspector's head and to the TARDIS, opening the door as the others watch. Smiling down at the Doctor, Chrstina happily tells him, "We could have been so good together", revealing no hard feelings over her rejection. The Doctor merely smiles back and replies, "Christina, we were." Christina flies off into the night, the other passengers cheering her off, the Doctor merely watching; the Doctor then heads into the TARDIS.

Cast

 * The Doctor - David Tennant
 * Lady Christina de Souza - Michelle Ryan
 * Professor Malcolm Taylor - Lee Evans
 * Captain Erisa Magambo - Noma Dumezweni
 * D.I Macmillan - Adam James
 * Lou - Reginald Tsiboe
 * Carmen - Ellen Thomas
 * Angela - Victoria Alcock
 * Barclay - Daniel Kaluuya
 * Nathan - David Ames
 * Bus Driver - Keith Perry
 * Sgt Dennison - Glenn Doherty
 * Sgt Ian Jenner - James Layton
 * Sorvin - Paul Kasey
 * Praygat - Ruari Mears

Production crew

 * 1st Assistant Director - John Bennett
 * 2nd Assistant Director James DeHaviland
 * 3rd Assistant Director Sarah Davies
 * Location Manager Gareth Skelding
 * Unit Manager Geraint Williams
 * Production Co-ordinator Jess van Niekerk
 * Production Secretary Kevin Myers
 * Production Runner Siân Warrilow
 * Drivers Malcolm Kearney, Wayne Humphreys
 * Floor Runners Nicola Brown, Alison Jones, Tom Evans
 * Contracts Assistants Kath Blackman, Lisa Hayward
 * Continuity Llinos Wyn Jones
 * Script Editor Lindsey Alford
 * Camera Operators Joe Russell, James Leigh
 * Focus Pullers Steve Rees, Jamie Southcott
 * Grip John Robinson
 * Camera Assistants Jon Vidgen, Tom Hartley
 * Boom Operators Jeff Welch, Bryn Thomas
 * Gaffer Mark Hutchings
 * Best Boy Peter Chester
 * Electricians Steve Slocombe, Clive Johnson, Ben Griffiths, Jonathon Cox
 * Stunt Co-ordinator Lee Sheward
 * Stunt Performers Kim McGarrity, Jamie Edgell
 * Wires Bob Schofield
 * Choreographer Ailsa Berk
 * Chief Supervising Art Director Stephen Nicholas
 * Associate Designer James North
 * Art Department Coordinator Amy Pope
 * Production Buyer Ben Morris
 * Set Decorator Julian Luxton
 * Props Buyer Adrian Anscombe
 * Standby Art Director Nick Murray
 * Design Assistant Al Roberts
 * Storyboard Artist Richard Shaun Williams
 * Standby Props Phill Shellard, Jackson Pope
 * Standby Carpenter Will Pope
 * Standby Rigger Keith Freeman
 * Property Master Paul Aitken
 * Chargehand Props Matt Wild
 * Dressing Props Martin Broadbent, Rhys Jones
 * Senior Props Maker Penny Howarth
 * Props Maker Nick Robatto
 * Practical Electrician Albert James
 * Construction Manager Matthew Hywel-Davies
 * Construction Workshop Manager Mark Hill
 * Construction Chargehand Scott Fisher
 * Scenic Artist John Pinkerton
 * Graphics BBC Wales Graphics
 * Costume Supervisor Lindsay Bonaccorsi
 * Assistant Costume Designer Rose Goodhart
 * Costume Assistants Barbara Harrington, Louise Martin
 * Make-Up Artists Pam Mullins, Steve Smith, Morag Smith
 * Casting Associates Andy Brierley, Alice Purser

Astronomical Objects

 * The bus is transported to the Scorpion Nebula on the other side of the universe.
 * San Helios became a desert over the course of a year or under. The sand is all that remains of the dead.
 * Barclay and Nathan mention the Stolen Planets.

The Doctor

 * Carmen makes a prediction for the Doctor's future using her psychic gift: "Your song is ending, sir. It is returning. It is returning through the dark. And then, Doctor, he will knock four times." This prophecy reflects the Ood's message to the Doctor, "Your song will end soon" and is possibly a reference to The Master with his mental drumming from "The Sound Of Drums/Last of the Time Lords".
 * The Doctor's TARDIS is discovered in the gardens of Buckingham Palace, and according to the Doctor, the Queen "doesn't mind". Previous stories implying that the Doctor and Queen Eilzabeth II know each other and are on good terms include Silver Nemesis and Voyage of the Damned
 * The Doctor said that he will "never" take another companion on board the TARDIS because he has lost all his previous ones.
 * The Doctor's psychic paper is compatible with the Oyster Card scheme used for public transport in London and he uses his psychic paper to 'pay' his bus fare.
 * A reference was made to Donna Noble as the Doctor said he had a friend who called him "Spaceman" (DW: Journey's End, et al).
 * Malcolm says he had read all the Doctor's files and the Doctor asked "Really? What was your favorite? The Giant Robot?" This is a reference to the Fourth Doctor-era story Robot.
 * The Doctor's Sonic screwdriver can be used to tint his glasses to look like sunglasses.
 * The Doctor admits that he stole his TARDIS from his own people.
 * The Doctor says Christina looks like a Time Lord, in response to her saying that he looks like a human. Although, it may have been more accurate for him to state that she "looked Gallifreyan" since that is the group name of the species he belonged to. Not all Gallifreyans are Time Lords, and not all Time Lords are Gallifreyans.
 * The Doctor tells Christina of some of the eras he's visited: World War I, the creation of the universe, the end of the universe (DW: Utopia), "the war" between China and Japan (exactly which war is not specified; possibly a reference to the conflict predating World War II); and the court of King Athelstan in the 10th century AD.

Foods and Beverages

 * The Doctor offers Christina the rest of his chocolate Easter egg because he's determined to keep his teeth.

Physics

 * The Doctor's device is attempting to detect Rhondium particles.
 * A wavelength parcel of ten kilohertz operating in four dimensions equals one Malcolm.
 * 100 Malcolms = 1 Bernard

UNIT

 * UNIT is called in by the police to assist in locating the bus.
 * UNIT has an automated phone system. Like most standard phone systems, however, pressing zero bypasses the automation and connects with an operator.
 * UNIT troops are equipped with H&K G36 assault rifles, M4 carbines, and Walther P99 pistols.
 * Malcolm's apparel as he leaves his laboratory is similar to that of the Doctor's fourth incarnation.
 * UNIT maintains extensive files about the Doctor.
 * The Captain expresses her surprise that "Guns work", a reference to the many past occasions in which UNIT encountered alien creatures impervious to standard firepower.

Other

 * Christina compares the bus to a Faraday cage.
 * Oyster cards, a form of electronic payment on London buses, are referenced, with Christina making a joke about them in an unsuccessful attempt to board the bus without paying, and the Doctor uses his psychic paper in lieu of one.

Story notes

 * The title of the episode was unveiled during the closing credits of The Next Doctor broadcast on 25th December 2008, several weeks before production of the episode was due to begin. The title of the next special, The Waters of Mars, was in turn officially revealed in a trailer included at the end of the closing credits of Planet of the Dead, although Davies had revealed the title in an interview broadcast a few days earlier.
 * This is the first Doctor Who episode in which series producer Russell T Davies shares co-writing credit, and the first episode since the show's return in 2005 to credit two writers. The last televised story to credit two writers was the 1993 mini-episode Dimensions in Time.
 * The casting of Michelle Ryan has been reported both by media and via on-set confirmation. Ryan, best known for her work on the UK soap opera EastEnders and the US science fiction series Bionic Woman, had previously co-starred in the Steven Moffat-written mini-series Jekyll and was also reportedly a candidate for new companion after the departure of Billie Piper in 2006.
 * After initial rumours, it was confirmed that part of the episode will be filmed in Dubai, United Arab Emirates through BBC News coverage that a bus that was to be used for filming there was heavily damaged upon arrival there.
 * According to the BBC report, the damage to the bus -- a twin to one being used for filming in Cardiff -- prompted a rewrite of part of the script, the recently released trailer for the episode depicts damage to the bus identical to the damage seen in many on-set photos, suggesting that the bus getting damaged has become part of the story.
 * On 16 January 2009 The Guardian newspaper published an online column condemning the then-rumoured plan to film in Dubai, citing the UAE's human rights record. Similar criticism was posted by the fan site Kasterborous on 28 January.
 * As seen in David Tennant's video diary for this episode's read-through, Tennant feared that, having spent six months portraying Hamlet for the RSC, that he would be unable to accurately replicate the voice he uses when portraying The Doctor. In an informal discussion with Julie Gardner, he describes his voice for Hamlet as being the same as the Doctor's (being an English accent) except "more posh" and mentioned he may have to watch his previous performances as the Doctor and practice the voice. This strongly echoes Billie Piper's dilemma when she returned to film Turn Left; in interviews with Doctor Who Confidential, Piper confessed to having forgotten how to speak in Rose's accent; it was later noted that she spoke with a noticeable lisp in several scenes of that episode.
 * It has been confirmed by the BBC that Planet of the Dead will be the first Doctor Who story to be produced in high-definition; this changeover can be likened to the move from black and white to colour production in 1970.
 * According to Tennant's video diary, he and co-star Adam James have been friends for 10 years, having also worked together in the past, James is also Jon Pertwee's godson.
 * In an interview for BBC Breakfast on 7th April 2009, Russell T. Davies revealed that the episode had only been completed at 11:30pm the previous night, only 5 days before the episode airs.
 * DWM Issue 407 confirmed that Planet of the Dead was Doctor Who's 200th story.
 * Lady Christina is the latest companion to kiss the Doctor.
 * In pre-broadcast publicity interviews, Michelle Ryan described her character as a one-off companion, though like most other one-offs, such as (initially) Donna Noble, and Jenny the door has been left open for a future return.
 * The advertisement on the side of the bus reads "Unbeatable global call tariffs". On the other side it says "Tomorrow is here" and both sides say "Neon by Naismith" with the company being Neon. It is possible that this a reference to the two final episodes of the 2009 Specials as actor David Harewood has stated that he will play a character called Joshua Naismith in David Tennant's final story.
 * Lady Christina de Souza is similar to a character called 'Kate Tollinger' who was to have been introduced in a story called Crime of the Century had Doctor Who been produced beyond Survival in 1989. Tollinger would have been a safe-cracking, lock-picking thief.
 * When discussing Easter, the Doctor claims to "remember the original". It's unclear whether this means he was present at the crucifixion and/or resurrection of Jesus -- the events the Easter season commemorates -- or the first actual celebration. If the former, this bookends an earlier statement made by the Doctor in Voyage of the Damned suggesting he was present at the birth of Christ.
 * As in the previous story The Next Doctor there are no scenes taking place in the TARDIS (although unlike The Next Doctor, the TARDIS interior is briefly visible in the background when the Doctor enters at the end).
 * The trailer for The Waters of Mars, which appears at the end of the credits, includes the sound of the cloister bell, the significance of which has yet to be revealed.
 * Although the Doctor has had invitations to join him turned down by potential companions in the past (Grace Holloway in the 1996 TV movie and, initially, Donna Noble in The Runaway Bride, for example), this is one of the only occasions in which the Doctor has outright refused to take on a companion of his own volition, despite clear indications of compatibility. This also occurred with Bayldon Copper in Voyage of the Damned, and for much the same reason the Doctor gives Christina.

Ratings
The BARB official ratings are 9.54 million, the 5th most watched programme of the week, the second most watched on BBC of the week and the second most watched of Saturday 11th April. It also gained 200,000 viewers on BBC HD, the biggest ever audience for the channel. Planet of the Dead is now the sixth best rated Doctor Who episode since its 2005 revival with Voyage of the Damned, The Next Doctor, Rose, Journey's End and The Christmas Invasion beating the episode.
 * Easter Saturday 11th April 2009 ~ 6:45pm ~ BBC One ~ 8.41 million (unofficial overnight)

Myths and Rumours

 * Carmen mentioned in "It is returning, he will knock four times" could be Davros, the Meta-Crisis Tenth Doctor or The Master.  Or it could mean something else entirely. The "knock four times" could refer to the Master, as the drumming motif that he continuously hears in his head, and that he used in The Sound of Drums/Last of the Time Lords to hypnotize the Earth's population, was a four-beat rhythm. Alternately, the "darkness" was used throughout the fourth series to refer to the return of Davros. His "song" may also be a reference to River Song, a future companion who appeared and died in Forest of the Dead; it may also be connected to the prediction of the Ood in DW: Planet of the Ood. The four knocks is also somewhat reminiscent of the Midnight Entity, a side note on that, the music from the episode Midnight was in the background as the Doctor was warned. Also when Carmen mentioned the "darkness" Davros's theme from the Season 4 finale was played.  Another possibility is that he is referring to the Eleventh Doctor "knocking" on the Doctor's door in a metaphorical sense, as in its the Eleventh Doctor's time now. Some belive that it is Galifrey that is returning through the dark. It is also worth noting that The Beast called the  darkness 'his domain'.
 * Since eccentric time lady Iris Wildthyme had a TARDIS that resembled a London bus, there were rumours she'd appear in the special.
 * Related to the Wildthyme rumor, speculation regarding the identity and true nature of Lady Christina, following statements by Davies that she would have a profound impact on the Doctor, included the possibility that she might be a Time Lord, and perhaps even a known Time Lord such as The Rani or Romana. This ultimately proved not to be the case, although the Doctor's comment to Christina, "You look Time Lord" (filmed in January-February 2009, after the speculation began) might be a reference to the rumor. The "profound impact" is likely the fact that the Doctor chooses not to make her his companion, despite their obvious compatibility.
 * Michelle Ryan is one of many young actresses rumored to be contention to appear as companion to Matt Smith's Doctor. In pre-broadcast publicity, Ryan stated she considered Christina to be a one-time companion.
 * The Radio station, Neon, advertised on the buses in London is part of the story arc for forthcoming episodes.
 * The bus used for the Dubai filming was stolen and needed to be replaced. There is no indication this is the case. It is a known fact that the bus shipped to Dubai was heavily damaged upon arrival and needed some restoration work, and according to media coverage there was talk of trying to replace the bus before the decision was made to alter the script instead, but no indication that any buses were stolen during production.

Filming Locations

 * Cardiff, St Mary Street - the first scenes with the red bus driving down the road with the Doctor and Christina stepping on to it
 * Cardiff Bay - Police and UNIT investigating the disappearance of the bus through the wormhole
 * Dubai, United Arab Emirates - San Helos

Discontinuity, Plot Holes, Errors

 * At the beginning of the story the wormhole is in the centre of the tunnel but by the time the bus driver dies it is at the entrance. The wormhole increases in radius, as the UNIT Captain says. It's not illogical to then assume the entrance and exit are further apart when they return.


 * Why do the International Gallery guards really not look at the item they're guarding? They were expecting intruders to enter from the sides, not from above or below, and therefore were keeping a lookout to the sides.


 * Would the security lasers around the relic in the museum not have a roof of some kind? Haven't they worked out that thieves can enter the museum from above? Perhaps they felt it wasn't needed, as they had four guards at the scene. Plus, seeing as this takes place in 2010, the recession may have caused the museum to cut down on the budget for security.


 * Why do none of the passengers on the 200 question why there are many Police Cars following them? They're in London, police are everywhere.


 * When the bus is originally shown, it has a number plate of W974GHM, but later, when flying, its number plate has changed to RUA467W. Two buses were used for filming, and the crew may have simply forgotten to change the plates. However, In-Universe, the point stands and it is a continuity error.
 * The Doctor claims that it will take the Swarm 20 minutes to reach them 100 miles away. So therefore they were moving at 300mph. However, when Christina was being chased by one it could not catch up despite her moving at a much slower speed. The one that chases Christina had only just got going. The ones creating the wormhole had been circling for days suggesting they have had time to build up speed. Also, the one that chased Christina was waking from hibernation and so may still have been dazed. It may have also been slowed down by the narrow passage. Furthermore, Christina was being pulled up by an electronically-powered winch that the Doctor obviously had on the fastest setting, which would have been fairly fast.


 * How exactly does Nathan phone the Doctor? The Doctor has only given free roaming to Barclay's phone. In Journey's End all the phones in England call the Doctor with only a few of them having free roaming capabilities. Obviously, if the Doctor enhances a phone, it can be contacted anywhere in the universe from any phone. A similar situation occurred in DW:The Sontaran Strategm, when Martha calls her old cell phone on the TARDIS from a different phone on Earth.


 * Why did the Tritovores have ear pieces? They clearly don't have ears. Not that we know of. Plus they may have used them through some other part of their body. Plus we don't know if the Tritovores had members aboard their ships who were humanoid in form and had ears.


 * The rays were traveling in a swarm; how did only three manage to get through when they were all going through together? Could have easily have been scouts/leaders, ahead of the swarm. However, I do agree they were quite far ahead and UNIT took a long time to close the wormhole. The time taken was probably exaggerated to build suspense though.


 * The bus is seen to take on damage as it travels through the worm hole, but on its way back to Earth, no more damage to the bus is sustained. On the way the wormhole was very small. When they return it was much bigger. The bus was obviously affected on the way there due to the size of the wormhole.


 * Surely companions like Jack Harkness or Martha Jones aren't exactly "lost"? The Doctor may be referring to his companions generally. They are lost to the Doctor as they now have there own lives. However, this episode does not follow directly from The Next Doctor nor do the two prior episodes (Journey's End and Music of the Spheres). There may have been lots of time in-between where something has happened to the other companions. It may also a mean Loss of his frienda that he was closest to and cannot risk that again .


 * Why did Carmen not see that they were going to survive? Because, like with time itself in the show, certain events are in flux, rather than fixed. Perhaps the Doctor saving them was in flux.
 * It's not an exact science. She doesn't see everything.


 * There are tire tracks behind the bus, proving it drove to its location. Or it skidded as it exited the wormhole, thus making tracks. The area around the bus was cleaned of all footprints, tire tracks and vegetation prior to the commencement of filming. Therefore any tire tracks were added in by the art department.


 * When Christina escaped the police car at the end, why didn't all the hundreds of heavily armed UNIT troops not try to stop her when she just ran past them? UNIT were either preoccupied with clearing up the 3 aliens, debriefing the bus passengers - or, UNIT simply does not get involved with police matters.


 * After seeing its fellow eaten why didn't the other Tritovore just shoot the stingray with its weapon. It might have been panicked and attacked the Alien Stingray instead of running. It looked like it tried to, but was too scared and got eaten before it could. Plus we do not know the relationship of the two Tritovore. If they were lovers or great friends then the other may have been just boldly fighting regardless of what happened to him.


 * The cannon the UNIT troops are using is seen being fired several times out of four nozzles but only one of the rockets seems to hit the Stingrays each time. Perhaps the cannon is a special cannon that only UNIT has that fire rocket parts which combines together in the air to form one rocket. One big rocket. Or maybe the other three launched just missed


 * Police cars can't be opened at the back from the inside, so how did Christina escape? The handcuffs may not have been the only thing the Doctor unlocked with his screwdriver.


 * Why didn't the Doctor just ask UNIT to send an all terrain vehicle or helicopter through the wormhole to pick up the survivors? Or other supplies for that matter? The Unit team could have had their vehicles damaged and/or stuck on the planet as well - then they would have had a much harder job getting everyone back.


 * Why is this the first episode to mention the recession, the episode is set in 2010, the recession should have been mentioned on the episodes DW: Voyage of the Damned, Partners in Crime and the two parters The Sontaran Stratagem / The Poison Sky and The Stolen Earth/Journeys End, which were set in 2009 (except for Voyage of the Damned, which was set in 2008)? History doesn't always match.  It may have happened at a different time, or people just thought that their were more important events (like the whole world being covered in smoke) than a recession. Or this is the start of RTD trying to put the series back into the present day. There is no indication this takes place a year after the events of Series 4 so this could too happen in 2009.  /But given that this episode is set on Easter Sunday, that would mean that all the episodes mentioned above would have taken place before the twelfth of April 2009, which even for the Doctor Who Universe, is too much in such a short space of time.


 * Early in the episode, it was shown that the worm hole was very close behind the bus in the desert. When the Docter flies the bus back in to the worm hole, he had to travel considerable distance before reaching it. When they first take off in the bus they celebrate that it worked before turning around and flying back to the worm hole. PLanetary drift could have also played a part in the wormhole's moving.


 * In the beginning when the bus entered the worm hole at ground level, it seems like it exited at or close to ground level on the other planet. When the bus flew back into the worm hole high above the ground, it ended up exiting at Earth very close to the ground when it should be much higher. As stated above, planetary drift could have caused the wormhole to shift slightly, making the exit point for the bus very different than before


 * The bus entered the worm hole from inside the tunnel and exited on the planet, yet reversing direction from the planet into the worm hole from the same side results in the bus (and other objects) exiting on Earth at the opposite side of the worm hole outside the tunnel when they should be exiting on the original side, inside the tunnel. Wormholes may function differently than tunnels; they are holes in space, so who knows what may happen inside them


 * Wormholes do not form by flying around a planet really fast in great numbers. It is explained how and why this happens in the episode. Saying that it is different to our science is rather like complaining that it's impossible to have an object that is bigger on the inside than the outside.None of the aliens really exist, none of the events really happen.  Use some imagination. PLus, we don't know what other factors were present along with the Stingrays


 * The chances of creating a wormhole with an exit on a planet is so improbable it is virtually impossible. Doctor Who science, anything is possible. The creatures probably aim their wormhole toward a planet. Perhaps the planets all had a magnetic field like earth's; as we don't know the commonalities of the planets, we can't say for sure


 * The tritivores can be heard emitting a number of very fast clicks and chirrups when their mouth appendages aren't even moving. Humans can make humming noises without opening their mouths...


 * It was obvious the bus was being followed by the police. Why didn't the driver pull over? He was afraid he would get arrested for helping an escaping fugitive, who payed him with diamonds. He could have known she was wanted by the police because a normal person would not pay in earrings. 

Continuity

 * As this episode is the 200th storyline of Doctor Who, the episode makes an in-universe reference to this by calling the bus The 200.
 * Several bus passengers discuss the events surrounding the relocation of Earth to the Medusa Cascade (per DW: The Stolen Earth/Journey's End), which places this story as taking place after those events, while confirming that, unlike the Battle of Canary Wharf, there seems to have been no attempt to "cover up" what happened, and it remains public knowledge.
 * The Doctor mentions "Humans on a bus, always blaming me", referring to DW: Midnight.
 * The Doctor mentions the K1 Robot that featured in DW: Robot, when asking Malcolm what his favourite file about him was.
 * UNIT at last meets an alien race that's not immune to bullets DW: Robot or as Captain Magambo puts it "I don't believe it, guns that work", this also refrences the events of The Sontaran Stratagem where UNIT's weapons are rendered useless.
 * Carmen says "Your song is ending" which is what the Ood also said to the Doctor in DW: Planet of the Ood. As well as the warnings of darkness heard in Series 4 (Turn Left, et al); the reference to knocking reflects a similar event that occurred in DW: Midnight and the drums the Master hears in DW: Utopia and DW: The Sound of Drums This could be a dark hint that the Master may have begun his return to power
 * Bernard Quatermass is mentioned and referenced, he was previously mentioned in DW: Remembrance of the Daleks.
 * Captain Mugumbo's exclamation "the guns work" could be a call back to the Brigadier who once proclaimed he hated how so many aliens were immune to bullets; or more likely a reference to UNIT's trouble in their last appearance DW: The Sontaran Stratagem / The Poison Sky.
 * When Christina calls the Doctor "Spaceman" he refers to Donna, saying "I had a friend that used to call me that"

DVD and Other releases
According to Amazon.co.uk, a Region 2 (UK) DVD and Blu-ray release is scheduled for 29 June 2009.It will include the one-hour Doctor Who Confidential behind the scenes look as a bonus. No official announcement has been made by BBC Video or 2 Entertain. 

In North America, the DVD and Blu-ray will be released on 28 July 2009. 

This will mark the first Blu-ray release for Doctor Who if it is released on Blu-ray as suggested by Amazon

International broadcast
The Canadian cable network, Space, has announced it will air the special on June 20, 2009, confirming that it is taking over broadcasts of Doctor Who from the CBC. The American network Sci Fi Channel, which holds the initial US broadcast rights to Doctor Who, has yet to announce an airdate for the special.