An evil, high-fashion designer plots to steal Dalmatian puppies in order to make an extravagant fur coat, but instead creates an extravagant mess.

Professor Phillip Brainard, an absent minded professor, works with his assistant Weebo, trying to create a substance that's a new source of energy and that will save Medfield College where his sweetheart Sara is the president. He has missed his wedding twice, and on the afternoon of his third wedding, Professor Brainard creates flubber, which allows objects to fly through the air.

Jack Powell suffers from an affliction that makes him grow four times faster than normal, so the 10 year old boy looks like a 40 year old man. After years of being tutored at home, Jack convinces his overprotective parents to send him to public school. The children don't know what to make of Jack, but with the help of his fifth-grade teacher, he makes an effort to win them over.