In Trip's Halloween party, the bat decorations look similar to the Batman logo. Trip's voice actor Michael Keaton was in Batman (1989).
Trip Larson is very similar to Mason Verger, the antagonist in Thomas Harris's novel Hannibal including the pig farming and antisocial behaviors.
This episode was produced during season 5, as evidenced by the "5ABE" production code, but it didn't air until season 7.