He appeared in the episode Claustrophobia. He showed to having an interest in Sissi in this episode, resulting in jealousy from Herb Pichon. Although in a Time Reversion, Odd instead sparks an interest in him towards Yumi in order to prevent rivalry between Theo and Herb. However, this also is shown to have made Ulrich jealous when Theo offers to walk Yumi home from a soccer game with his arm around her.
Theo continued appearing from the second season, appearing regularly without much importance. He speaks in "Tip-Top Shape". In "The Lake", after an electric shock, he exclaims to Jim that he is afraid. He was possessed in "Bad Connection".
In Code Lyoko Evolution, X.A.N.A. created a spectre of a boy with a very similar appearance with Theo in the episode How to Fool X.A.N.A. to hypnotize Yumi into giving him her codes. It is ambiguous if this was supposed to look like Theo or not.
- Lyoko Minus One
- False Lead
- Temporary Insanity
- Nobody in Particular
- Double Trouble
- Final Round
- William Returns
- Double Take
- Wreck Room
- Maiden Voyage
- I'd Rather Not Talk About It
- The Lake
- Lost at Sea
- Lab Rat
- Guided Missile
- Kadic Bombshell
- Music to Soothe the Savage Beast
- Bad Connection
- Fight to the Finish
- In Polish version of the show he was voiced by Leszek Zduń.
|Jeremie Belpois | Aelita Schaeffer | Odd Della Robbia | Yumi Ishiyama | Ulrich Stern | William Dunbar|
|Sissi | Jim Morales | Suzanne Hertz | Anthea Schaeffer | Mr. Delmas | Laura Gauthier | Franz Hopper|
|Kiwi | Herb Pichon | Nicholas Poliakoff | Amelia "Milly" Solovieff | Tamiya Diop | Hiroki Ishiyama | Johnny | Takeo and Akiko Ishiyama|
|X.A.N.A. | Monsters|
|Professor Tyron | Ninjas | X.A.N.A. William|
|Jean-Baptiste Pujol | Theo Gauthier | Emily LeDuc | Taelia | Samantha Knight | Samantha Suarez | Heidi Klinger | Mathias Burrel | Magali de Vasseur | Claire Girard | Brynja Heringsdötir | Patrick Belpois | Romain Le Goff|
|X.A.N.A. Aelita | X.A.N.A. Odd | X.A.N.A. Yumi | X.A.N.A. Ulrich | X.A.N.A. Franz Hopper | X.A.N.A. Anthea Schaeffer | Jeremie Clone | Aelita Clone | William Clone | Subdigitals|