anon for this: There is another ending for your joke. It goes like this:
This guy is listening to a group of people chatting and laughing. They are enjoying themselves so much that he listen in and realizes that they aren’t having an actual conversation. Instead, one person calls out “number 9” and everyone laughs, then as soon as they stop laughing another person calls out “number 32” and they all crack up again. So the guy asks one of the group what’s going on, and he says, “We’re such old friends that we already know each others jokes, so we just refer to them by number instead of telling the whole joke.”
Suddenly one man calls out “77” and everyone starts laughing as if there is no tomorrow. The eavesdropper turns to someone in the group, and asks, why is everyone laughing so hard at this joke? The member replies, “dis one? dis one we haven’t heard yet.”