Code Lyoko (2003)

Season 1: Episode 1

A student named Milly seeks the comfort of her teddy bear after being embarrassed and ostracized due to her young age by Sissi, the school's bully/diva. Milly believes that her teddy is the only one that she can turn to for comfort and support. A corrupted super computer known as X.A.N.A. enters the real world by possessing the bear. In a quest to strike and destroy his enemies, the X.A.N.A infected teddy bear increases to an enormous size. No one is safe as this monstrosity creates a path of destruction.