The Grimleys (1999)

S2E18 Fester Goes on a Diet

Uncle Fester is secretly preparing for a visit from his pen pal Yvette, who works at the Folies Bergère, by attempting to get in shape. He even enlists the help of fitness icon Jack LaLanne. As Fester embarks on this unexpected journey of dieting and exercise, Morticia and Gomez become suspicious. However, they mistakenly assume that Fester is gearing up to join a space program instead.