Season 5, Episode 14: Lisa vs. Malibu Stacy
Over the course of The Simpsons, Grandpa Simpson is often shown to be a big fan of writing letters to people, companies, and publications, usually to complain about something. In the episode “Lisa vs. Malibu Stacy,” Grandpa realizes he’s nearing the end of his life and decides to give his family their inheritance early so he can see them enjoy it. Since he knows Lisa enjoys reading, he decides to give her his lifetime of personal correspondence. Lisa takes a telegram from the pile and we learn that at one point in time, Grandpa had many things to say to Boris Karloff, who was apparently not amused.
