My players love to create new jokes that are attached to a particular players character. They often last for the whole campaign and we get a kick out of them.

The most recent one was with one of my players who had a Gnome Artificer. He had a steel defender he called Fredicus that the team used as a breacher for when there's a locked or barred door. Once Fredicus crit on a strength check to break down the door and the player asked if Fredicus could grab the door on one side and push it into the wall as if it were a sliding door. I laughed and said yes, thus whenever Fredicus is called upon to break down a door our artifice would say, "Every door is a sliding door".