The castle thunder is a running gag sound effect that is used throughout the original Hillenburg era episodes. It is first used in the popular 1932 film Frankenstein. It simply a loud thunderclap near a castle. This sound effect was used in some shows before and after the series was created. It is mostly used in some Hanna-Barbera, classic Disney movies, classic Nelvana cartoons, 70s, 80s, and 90s cartoons. There is also an alternate version, which was only used in The SpongeBob SquarePants Movie. It is similar to another running gag, "My Leg!"