Crustacean Crime Theater is a TV show that only appears in the episode "Life of Crime." It is a show in which crustaceans commit crimes and is watched by SpongeBob, Patrick, and Mr. Krabs in the episode. The latter shows an episode of the series to the former two as a means to educate them to never steal.
NOTE: This won't describe the whole series, but rather all that is shown in the episode in here, meaning there might be more than this.
In the show, a mean hermit crab (possibly the Sneaky Hermit) steals a sleeping hermit crab's shell. Said sleeping hermit crab wakes up and tells police that a hermit crab stole his shell. The police catch him and put him in jail.