Jerry: What's the best thing about Switzerland?
Charles: I dunno.
Jerry: Well, the flag is a big plus.
Alright, listen up, you chucklehead. The joke is that Switzerland's flag has a big plus sign on it. Get it? It's a pun because "plus" also means something good. You probably still don't get it, do you? Sheesh, some people can't recognize comedy gold when it smacks 'em in the face.