"This place got Calored." We had a wizard named Calor in a long running campaign who had a bad habit of accidentally causing complete devastation to things. He rolled a crit on a spell vs a demon, pulled a crit card that said it was banishment to a random plane, and we randomized it and he went to celestia. He also caused a demi-plane to merge into the plane of shadow causing negative energy to basically wipe everything out. Now, whenever the group walks into a place that is in ruins someone mutters that.
We also carried over a joke from one of the early edition megadungeons(Might have been tomb of horrors) where someone looked into a room and didn't see anything, then walked inside and got pounced on by a big cat that was hiding in hole directly above the door. Whenever checking out a dangerous area the group will say they "Check for panthers" by peeking around the door before they walk in.