Every 911 joke isn't that good.
Well, at least not until they come crashing down.
Alright, listen up, buttercup. This joke is about 911, like the emergency number. But it also refers to the September 11 attacks, where planes crashed into buildings. The joke is saying 911 jokes aren't funny until you think about the planes "crashing down" during the 9/11 attacks, which is a dark and edgy.