Ian Failes of FXGuide has written an informative overview of how SpongeBob and company were translated from hand-drawn designs to CGI, and then composited into their live-action setting for the film The SpongeBob Movie: Sponge Out of Water.
Glenn Melenhorst, vfx supervisor at Australian studio Iloura, explained to FXGuide that for the CG versions to match their 2D counterparts, they had to replicate the stylized animation approach of the TV series, which emphasizes strong poses and snappy movement:
“We studied as much SpongeBob as we could understanding their beats, both of acting and stillness, understanding how long to transition from pose to pose and how much to overlap the action. One thing we noticed was that SpongeBob seldom rotated smoothly in cel animation. As soon as his rectangular head rotated digitally he looked very wrong, so taking cues from the 2D animators, we turned him snappily, often with a compression of his body or animated accent.”