Summary: Darrin, skipping his Sunday golf to work on a slogan for Larry's new account, TOP-POP, sees Samantha's Uncle Arthur standing in the mirror. Arthur pops out, Darrin yells, and Samantha orders the zany Arthur back into the mirror. Arthur pops back in and the mirror shatters. Despite Darrin's pleas, Arthur pops in and out of every mirror in the house, breaking each one. Samantha decides Arthur is ill and summons Dr. Bombay. Larry drops by to see how Darrin is progressing and Samantha has a time explaining a palm tree that Arthur has grown in the living room. Darrin gets Larry out of the house and then decides to sneak off to play a few holes himself.
The pill Dr. Bombay gives Arthur has side effects - Arthur immediately becomes everything he happens to think of. He turns into a pony, a devil, and an Indian. Samantha takes him for a drive to calm him down and Arthur declares the fresh air makes him feel like a superman. Immediately, he appears in Superman's outfit and takes off into the sky. There is chaos in the neighborhood as Arthur zooms around, and when he lands on the Stephens' roof, the police are waiting. Larry and Darrin also arrive and Samantha suggests it is all a stunt to publicize Darrin's new slogan - "Try TOP-POP, it's super, man!" Larry and the police think it's a great idea and everything returns to normal. Until Uncle Arthur takes another pill and pops all the furniture out of the house.