Code Lyoko - Season 2 Episode 16
A Fine Mess

After a malfunction and a little bug with the regular materialization program, Odd and Yumi are bugged up, ending up in each others bodies. Even worse, their atoms start splitting after a while due to being dematerialized, even on Lyoko. The gang has to go to Lyoko and fix the problem before Odd and Yumi disintegrate and disappear forever, but its not easy when Xana tries to stop them.