Amnesia

Using a new machine in the school's physics and chemistry lab, X.A.N.A. manages to create nanoviruses, tiny machines capable of attacking memory cells in the human brain. Our heroes are X.A.N.A.'s principal targets, and Ulrich is the first one to go down. Seeing that her heart's desire is suffering from amnesia, Sissi takes full advantage of the situation : she fools him into thinking that she is his girlfriend, and that Odd, Yumi and Jeremy are his sworn enemies... It's a difficult situation, all the more so because the nanoviruses are starting to affect the whole population! Luckily, our heroes can once again join forces on Lyoko and save the world from amnesia!

Jeremie Belpois, Ulrich Stern, Odd Della Robbia, Yumi Ishiyama, Aelita, X.A.N.A., Elisabeth "Sissi" Delmas, Dorothy, Mrs. Suzanne Hertz, Herb Pichon, Nicolas "Nick" Poliakoff, Jim Morales, Tamiya Diop, Milly Solovieff, Jean-Pierre Delmas, Kiwi, Emily

There are 52 episodes planned.

Air dates shown are for those in the U.S. on Cartoon Network. In fact, the series first aired on France 3 on September 3, 2003.