From Fish Hooks Wiki
Halloween is an event celebrated on October 31st every year.
One year, the fish of the fish tanks in Bud's Pets, tired of Jocktopus Vandenbush stealing their candy, trick-or-treated outside the tanks. The plan failed, however, when Randy Pincherson, one of the trick-or-treaters, was discovered to have lead Jocktopus to them the whole time. ("Halloween Haul")
- Halloween at Wikipedia