With their mission complete, Lilo gets ready to say goodbye to her extended family from outer space, including Stitch. However, they must reunite to combat their nemesis Dr. Hamsterviel and a new threat, an experiment named Leroy.

Sid is trying out his new dance on his hardwood floors when he discovers that friction prevents him from sliding. When he plays ball, he quickly learns that if a ball doesn't have enough elasticity, it won't bounce. This calls for some investigating; after pretending to be 'Super Sid' by kicking the ball with all his might, Sid and his friends take a trip to the Science Center to investigate how using lots of force makes things move far and fast....