Fester Goes on a Diet is the eighteenth episode of the second season of the original series of The Addams Family, and the fifty-second overall episode of the series. It first aired 14 January 1966 on ABC.
Pugsley has been exercising, much to his parents' disapproval. Uncle Fester gets a letter from his French pen-pal, Yvette, who is coming to visit. He decides he has to get into shape too, but trying zen yogi in his bedroom doesn't work. He wakes up early to exercise with TV fitness guru Jack LaLanne, but Gomez and Morticia are appalled and give the television set back to the junkman. LaLanne comes to the house and gives Fester an astronaut training book to follow. Meanwhile, Gomez and Morticia can't understand why he's doing this and think he's ill. They call in Dr. Motley, who panics at some of the results when he tests Fester and flees. Morticia questions Fester under hypnosis and comes to the mistaken conclusion he wants to become an astronaut. NASA isn't amused when she tries to talk them out of employing Fester, since they have no idea what's going on. Fester goes down to the play room and uses the sarcophagus as a steam cabinet to lose weight. When Morticia and Gomez find him there, he finally explains about Yvette. When she arrives, she's rather overweight and jilts Fester because he's too skinny!
- Pugsley has a girlfriend named Marie.
- When Thing snatches the mail from Mr. Briggs, he is a left hand instead of his usual right.
- The moose's head is mentioned.
- Cousin Slump, Grandpa Squint and Cousin Blob are mentioned.
- Eye of Newt
- Puree of Aardvark
- Roast Yak