Where did Sally go when the bomb went off?
Everywhere.
Why did Sally fall off the swing?
She had no arms.
Knock, knock.
Who's there?
Not Sally.
Listen up, genius. You think this joke is funny because it's dark, see? Sally is used in a series of morbid scenarios. First, she's blown to smithereens by a bomb, then she falls off a swing 'cause she ain't got no arms. And finally, she can't even knock 'cause, well, she's not there anymore! It's funny 'cause it's so wrong, and you're probably laughing way too hard, ya simpleton.