Each of the Lyoko Warriors has an Avatar. Jeremie's Avatar has not yet been shown.
An Avatar is created by the Supercomputer whenever a new person enters Lyoko for the first time. Before the person first arrives on Lyoko, the picture on their ID Card shows a generic "person" icon. Jeremie hypothesized in "X.A.N.A. Awakens" that the Supercomputer is able to do this by taking the subconscious desires of a person and projecting them in the form of an Avatar.
An Avatar contains information about the person's Life points, weapons, etc. Avatars contain the Lyoko Warriors' ID Cards as well. Avatars, according to Jeremie in Revelation, are stored within the restricted access part of the Supercomputer, so their minds can't be directly possessed by X.A.N.A. unless their programming was modified.
The Avatars have been upgraded and changed over time.
- Ulrich's model changed drastically from Garage Kids to Season 1. His pants switched from a poofy 70s design to a streamlined look. His Katana also changed designs.
- Ulrich had an eyepiece in Garage Kids, but it was removed.
Changes between Seasons 1 and 2
- Yumi gained a second Tessen Fan.
- Odd lost Anticipation because Jeremie determined it was useless, as revealed in Triple Trouble.
Changes between Season 2 and Season 3, and during Season 3
- Aelita gained Energy Fields.
- Jeremie and Odd experimented with Teleportation, but it went really poorly.
Changes during Season 4
- William's avatar was completely redesigned as a byproduct of X.A.N.A. possessing him. He also gained Super Smoke.
- Jeremie reprogrammed Aelita's avatar to have wings and a different design. She ended up with a pink bodysuit with a mini skirt and different makeup.
- Ulrich's suit was redesigned, and he gained a second Katana. He switched from Joker Samurai to a yellow and brown design.
- Odd's new design had the same color palette, but a different layout. The cat ears were also altered.
- Yumi's new design had less pronounced makeup, slightly redesigned fans, and a new suit with a magenta and dark purple design.
Changes during Code Lyoko Evolution
- Due to the changed animation software, and cost, Code Lyoko Evolution saw much more latex-like designs.
- Odd's Laser Arrow launchers became retractable.
- Yumi gained the Bo Staff.
- William no longer had the Eye of X.A.N.A., but he retained the new color palate and powers.
- Aelita and Ulrich's designs lost their details.
- In "Countdown", Jeremie gave Odd an Eyepiece.