Season 4, Code Lyoko Wiki

The fourth season of Code Lyoko originally aired from May 18, 2007 to November 17, 2007. It mainly focused on the group traveling the Internet in search of X.A.N.A., in their virtual submarine: the Skidbladnir. Using their ship, they go searching for Replikas to destroy them to prevent X.A.N.A. from succeeding in world domination. They also try to rescue a X.A.N.A.-fied William and bring him back home. After the Core of Lyoko is destroyed, the group searches for a way to rebuild Lyoko once more

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Ulrich Season 4 Wallpaper by FireLordWael on DeviantArt

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List of Episodes, Code Lyoko Wiki