An eyecatch is a short animated clip which generally plays before or after a commercial break. They are also included in the video games Get Ready to Virtualize, Fall of X.A.N.A., and Quest for Infinity.
Each has one of the main characters' faces and their virtual avatar in the corner. Jeremie and Aelita (prior to The Trap) are the exceptions since Jeremie's avatar is never shown and Aelita's real-world form is not seen until Code: Earth. Since Season 2, most characters also received an alternate eyecatch that shows them on their vehicle. In Season 4, they were all updated for the new costumes.
No official eyecatch was made for William. Code Lyoko Evolution features transitions displaying the Eye of X.A.N.A. instead.