Thornton Melon (Rodney Dangerfield) is concerned that his son Jason (Keith Gordon) is unsure whether to go to college, so the uneducated self-made millionaire encourages him by signing up as a student as well. As Jason tries to establish himself among his peers and make the diving team, Thornton falls for a pretty professor (Sally Kellerman) and gets others do his schoolwork for him. When the suspicious dean (Paxton Whitehead) finds out, Thornton needs to show he can get by on his own.
Daniel (Ralph Macchio) moves to Southern California with his mother, Lucille (Randee Heller), but quickly finds himself the target of a group of bullies who study karate at the Cobra Kai dojo. Fortunately, Daniel befriends Mr. Miyagi (Noriyuki “Pat” Morita), an unassuming repairman who just happens to be a martial arts master himself. Miyagi takes Daniel under his wing, training him in a more compassionate form of karate and preparing him to compete against the brutal Cobra Kai.