Knock, knock.
Who's there?
A dragon.
A dragon who?
The dragon gonna drag its balls across your face.
Listen up, numbskull. You think knock-knock jokes are just innocent fun? Nah, this one takes a dark turn real quick. It lures you in with a typical setup, then hits you with a crude punchline about a dragon dragging its junk all over your face. Get it? It's funny 'cause it's nasty and unexpected, you walnut.