Ranma ½ (1989)

S1E159 The Tendo Dragon Legend

On their way back from school, Akane and Ranma stumble upon an unusual fish in a puddle. Dr. Tofu advises Ranma to take it home for a school project. Meanwhile, Kasumi extends an invitation for Dr. Tofu to stay with them due to an impending tsunami. Upon returning home, they discover that the fish is, in fact, a baby dragon. Dr. Tofu uncovers the secret that the dragon's meat can provide immortality. Just then, the Frogman (from episode 100) makes an appearance, intent on consuming the dragon's meat.