Jack Putter feels funny today, nothing new to this 25 hour-a-day hypochondriac. What's new is that Jack hears something. "I'm possessed!" he cries. And you're about to be possessed- by laughter. The voice Jack (Martin Short) hears is that of hotshot Navy pilot Tuck Pendleton (Dennis Quaid), subject of a secret miniatuization project gone awry and accidentally injected into Jack. And before frazzled Jack can say "I've got you under my skin", his unlikely partner propels him into the craziest escapade of his life.