however, including the line “that’s the Vatican coat of arms” makes the delivery worse for people who know of Vatican City and its flag, which sours the joke

The whole Simpson’s thatsthejoke.jpg is used to imply that everyone but the recipient gets the joke. That’s the whole thing right there.

Who’s the idiot, me for understanding that most people won’t get the reference, or people acting as if I’m the only person not getting it?