Alien Avatar was the twelfth episode of K9. It was written by Graeme Farmer, directed by Karl Zwicky and featured John Leeson as K9 Mark 2, Keegan Joyce as Starkey, Philippa Coulthard as Jorjie Turner, Daniel Webber as Darius Pike and Robert Moloney as Alistair Gryffen.
The Thames is badly polluted by an alien chemical. K9 discovers that telepathic aliens, the Medes, are imprisoned by Drake, who is trying to duplicate a missing special key to operate their organic starship. K9 rescues the Medes. June discovers Drake's plot and helps release their starship.
As they make their way to the River Thames, Starkey explains fishing to K9. Two CCPCs ask them what they are doing and K9 explains fishing to them. Starkey and K9 arrive to find dead fish. K9 warns him not to touch them, as he has detected an unknown alien substance. Starkey picks one up with his fishing net so he can bring it back to the Manor to analyse and accidentally bumps K9 with the fish. This causes a corrosive spot to start on K9. At Gryffen Manor, Jorjie sings along to music and accidentally elbows Darius, who is carrying a pile of books. Gryffen asks him if he was going to sell the books. Darius denies it, but Gryffen tells him to take them back to the library. Jorjie starts singing again and Gryffen has to raise his voice to get her attention to tell her to keep it down.
As Darius goes to the library, he sees two aliens appear and vanish. At Gryffen house, Starkey takes readings of the toxin in the dead fish. It is extraterrestrial. Starkey finds a match: the toxin is chenium, a corrosive byproduct of the manufacture of Qualon 37, used in the making of inter-dimensional starships. K9 estimates that if it builds up in the food chain, 85% of life in the Thames Valley will die.
In June's office, Drake orders a CCPC to be more persuasive. June tells him she sent her squad to investigate possible alien activity, but they were turned back by Drake's unit. Drake is contacted by the CCPC, who tells him the aliens won't stop talking. Drake tells June he won't "upset" her squad again. He has business to attend to. She leaves.
K9 and the team find where the toxin is entering the river. Starkey sees the aliens. They knock him to the ground and disappear. Back at Gryffen's house, K9 looks up the aliens in his file. They are the Medes, a species who can project their images as avatars if they cannot physically be present. The team decide to go to the pollution's source. K9 goes through the drains as Darius and Jorjie track him through the streets and Gryffen and Starkey monitor them.
K9's transmission starts to break up. In Drake's office, June finds the missing schematics for a Fallen Angel on his computer. When Drake arrives, she asks him about his interest in the ship. Before he leaves, she warns that he better not be in possession of the ship. June goes to Gryffen's house, where she shows him a blueprint of the Mede starship and the molecular refractor on the top, telling him Drake, not the Department, is exploiting it. The molecular refractor allows the ship to dematerialise and with this he could spy anywhere and not be seen.
The gang spots a factory. Gryffen and June analyse an image of the Mede avatar which cannot be seen in infrared. Starkey insists that Gryffen tell June the situation. Gryffen informs her that Darius, Jorjie and K9 are looking for the source of the pollution in North West 12. June contacts Jorjie and warns her to get out, but she and Darius are caught by CCPCs.
Darius and Jorjie are tied up in the factory, where Drake's men are experimenting with the refractor. K9 sees the Medes' avatars, who tell him to come with them. He replies in their language. They take him to the factory, the source of the pollution, where he sees the workers casting chenium. He finds Darius and Jorjie and frees them. Darius and Jorjie are recaptured. June arrives, takes control of the CCPCs, and the CCPCs take the workers away.
K9 asks Starkey to help him deliver the molecular refractor to the Medes and tells June that Drake had the Medes locked up. K9, Starkey and June gives the Medes the refractor, apologise for what Drake did to them and let them go. The Medes clean up the pollution and repair the damage to K9 before they leave in their ship. After noting the "awesome" day they had, Starkey asks K9 if he wants to go fishing. K9 cheerfully refuses.
- Professor Alistair Gryffen - Robert Moloney
- Starkey - Keegan Joyce
- Jorjie Turner - Philippa Coulthard
- Darius Pike - Daniel Webber
- Voice of K9 - John Leeson
- June Turner - Robyn Moore
- Drake - Connor Van Vuuren
- Foreman - Brian Bolton
- Mede 1 - Kristin Rolles
- Mede 2 - Lani Surverson
- CCPC - Marcel Baum
- CCPC - John Devine
- CCPC - Timothy Humphries
- CCPC - Robert Cooney
- CCPC - Favian Ledesman
- CCPC - Joshua Norbido
- CCPC - Jarrod Grodecki
Robert Moloney, Keegan Joyce, Philippa Coulthard, Daniel Webber and John Leeson are all credited in the opening of the episode and not the closing credits. With the exception of Leeson's credit, they are credited only by their name and not with their respective character's name attached. Additionally, on the DisneyXD broadcast, the Support Cast credits were omitted.
- Writer - Graeme Farmer
- Director - Karl Zwicky
- Producers - Penny Wall, Richard Stewart, Simon Barnes
- Executive producers - Jim Howell, Grant Bradley, Steve Robbins
- Associate producers - Bob Baker, Paul Tams
- Supervising producer - Dale Bradley
- Co-Executive producer - Mark Blythe
- With special thanks - Sam Tromans
- Line producer - Pam Collis
- VFX Director - David Napier
- Series Production Designer - Jon Dowding
- Episodic Designer - Adam Head
- New K9 Design by - Paul Tams, Alex Kubalsky
- Series Director of Photography - Ben Nott
- Episodic Director of Photography - Tony O'Loughlan
- Music by - Christopher Elves
- K9 theme music by - Michael Lira
- Editors - Russell Maggs, Strutts Pysros
- Casting - Faith Martin and associates
- Episodic casting - Lisa Maloney
- Drama/Dialogue coach - Peter Kent
- Story Producer - Greg Walters
- Script Adaption - Michaeley O'Brien
- Production Accountant - Pru Donovan
- 1st Assistant Director - Peter McLennan
- Script Supervisor - Sue Ketchington
- Costume Designer - Joanne Thompson
- Makeup Designer - Sharon Robbins
- Puppeteer - David Pawsey
- Location Manager - Charles Boyle
- Sound Recordist - Ian Grant
- B Camera Operator - Dan Maxwell
- Gaffer - Steve Monk
- Key Grip - Billy Harmer
- Special thanks to - Space Furniture, Shredox, J. Barbour & Sons Ltd, Heath Williams at Firefly Lighting, Videopro
- Safety Supervisor/Stunt Coordinator - Danny Baldwin
- Transport Manager - Alister Ward
- Unit Manager - Graeme Suhr
- Post Production Facility - Cutting Edge Australia
- Head of Post Production - John Lee
- Sound Design - Warren Pearson
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- This episode aired on the same day as the Doctor Who episode TV: Flesh and Stone.
- This episode establishes that the reason K9 Mark 2's language is laced with so much English slang is that the five thousand Earth movies on his memdrive have influenced his mode of expression.
- This episode definitively establishes that K9 has some sort of on-board linguistic database, as he talks to the Medes. This point was never particularly clear in his usage in Doctor Who, since he would have ostensibly had access to the Doctor's TARDIS translation circuit. Moreover, he's never been shown to use other languages in The Sarah Jane Adventures.
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Home video releases
This episode is featured in the following DVD sets:
- Series One complete box set, released in Australia on 29 September 2010. 
- A "vanilla" DVD called Alien Avatar, containing The Fall of the House of Gryffen, Jaws of Orthrus, Dream-Eaters, Curse of Anubis, Oroborus and Alien Avatar, released in Australia on 1 December 2010. 
- K9: Series 1: Volume 1, containing episodes 1–12, released in the UK on 31 January 2011 and in the US on 30 March 2011. , 
- K9: Ultimate Collectors Edition, containing the full first series, was released in the UK on 11 June 2012.