Ranma ½ (1989)

Season 1: Episode 159

While on their way home from school, Akane and Ranma discover a strange fish in a puddle. Dr. Tofu tells Ranma he should take it home and use it for a class project he has to do. Kasumi invites Dr. Tofu to come stay with them because of the tsunami that is about to hit. Once they get home, they realize the fish is actually an infant dragon. Dr. Tofu learns that the dragons meat will grant immortality, and the Frogman (from episode 100) arrives and tries to eat the dragons meat.