An inside joke can keep being repeated after one participant stops finding their role funny.

A running joke can outlast one person’s enjoyment of their part in it. The role was funny once, the group kept it, and now it is a fixed position that is difficult to object to without seeming humourless. Repetition converts a joke into a role and roles are hard to resign from.

Watch for the person in your group whose part in the joke has stopped landing for them. And if it is you, saying it once, quietly, to one person rather than to the room, almost always works. Most groups will drop a joke immediately when told, and almost none will notice on their own.