The Power of Three (TV story)

 was the fourth episode of the seventh series of Doctor Who produced by BBC Wales.

Synopsis
There have been many ways to invade the Earth, and the Doctor has seen them all – or so he always thought. And then the human race wakes up one morning and discovers the world has been overrun by… small black cubes. Which then proceed to… do nothing at all. A plan is afoot, humanity is endangered – but by what and how and, above all, when?

For the first time in his world-saving career the Doctor has to call upon one of the least of his virtues: patience. And the Ponds face something possibly more terrifying than any world-ending apocalypse: the Doctor is moving in!

Plot
to be added

Cast

 * The Doctor - Matt Smith
 * Amy Pond - Karen Gillan
 * Rory Williams - Arthur Darvill
 * Brian Williams - Mark Williams
 * Kate Stewart - Jemma Redgrave
 * Shakri - Steven Berkoff
 * Ranjit - Selva Rasalingam
 * Laura - Alice O'Connell
 * Arnold Underwood - Peter Cartwright
 * Orderly 1 - David Beck
 * Orderly 2 - Daniel Beck
 * UNIT Researcher - David Hartley

Uncredited cast

 * Brian Cox - Himself
 * Lord Sugar - Himself
 * Emily Maitlis - Herself

Communication technology

 * Kate mentions Flickr, YouTube and Twitter.

Game consoles

 * The Doctor plays tennis with the Wii.

Music

 * The song Merry Xmas Everybody by the rock band Slade is briefly heard in the hospital.
 * One of the cubes plays the infamously irritating Chicken Dance song (aka The Birdie Song), on an endless loop.

Culture

 * When Amy calls the Gallifreyan bedtime story about the Shakri weird, the Doctor remarks "You can talk. Wolf in your grandmother's night dress?" in reference to the story Little Red Riding Hood.
 * The Doctor tells Amy "Through the looking glass, Pond" in reference to Through the Looking Glass by Lewis Carroll.

Energy and radiation

 * Kate traced Artron energy levels to find the Doctor and then identifies him due to his fashion sense and double hearts.

Foods and beverages

 * The Doctor states that he invented the Yorkshire Pudding.
 * The Doctor, Amy and Rory eat fish custard.

Individuals

 * When Brian asks the Doctor what happened to those who previously travelled with him, he tells him that some left him, some got left behind, and some died.
 * Amy accidentally marries Henry VIII.
 * While playing virtual tennis, the Doctor speaks about the tennis player Fred Perry and a pair of shorts he took from him.

Species

 * There were Zygon duplicates at the Savoy when Amy, the Doctor and Rory visit.

Story notes

 * The working title for this episode was Cubed.

Ratings

 * The episode received an overnight viewership of 5.49 million people in the UK.

Filming locations
to be added

Production errors

 * When the Doctor observes the cube surfing the internet on the television, you can see someone outside the window behind the television. In other shots in that scene, there is no one outside the window behind the television. (It's Brian arriving at the house, he walks through the front door a few seconds later.)
 * In some shots when the cubes are counting down from 7, some cubes are missing the numbers in one shot and then have them in the next.

Continuity

 * Rory's father Brian reappears. (TV: Dinosaurs on a Spaceship)
 * The Eleventh Doctor, Amy and Rory have fish custard. (TV: The Eleventh Hour)
 * Kate Stewart is the daughter of Brigadier Alistair Gordon Lethbridge-Stewart. She previously appeared on-screen in HOMEVID: Downtime and HOMEVID: Dæmos Rising. She shortened her family name when she joined UNIT as she wanted to be judged on her own merits. Her appearance marks the first time that a character introduced in a direct-to-video spin-off reappeared in the television series. As Head of Scientific Research, Kate Stewart's role in UNIT combines that of scientific advisor, held by the Third Doctor and Fourth Doctor, with that of Commanding Officer held by her father.
 * Ten years have passed since the events of The Eleventh Hour in Amy's personal timeline.
 * The Doctor, talking to a flying cube, says "Is that all you can do? Hover? I'd a metal dog that could do that" referring to K9 Mark IV (and possibly to K9 Mark 2).
 * The Doctor once again asks how humans cope with just one heart. (TV: The Shakespeare Code)
 * Twitter is mentioned again. (TV: The Girl Who Waited)
 * The UNIT base beneath the Tower of London is visited. It was previously mentioned in TV: The Christmas Invasion and The Sontaran Stratagem.
 * The Ponds' anniversary takes place. They were married in Leadworth on 26 June 2010. (TV: The Big Bang)
 * A voice interface was last seen in TV: Let's Kill Hitler.
 * Rory kisses the Doctor on the cheek. The Doctor previously kissed Rory on the mouth in Dinosaurs on a Spaceship.
 * Whilst hiding from Henry VIII, the Doctor is holding a Mobile phone charger, which is apparently dropped as he sneezes. (TV: A Town Called Mercy)

DVD releases
to be added

Blu-ray releases
to be added