Why did Sarah call off the swing? Because she has no arms.
Knock knock. Who's there? Not Sarah.
Listen up, buttercup. The joke is funny because it's unexpected. Sarah can't swing because she ain't got no arms! And the knock-knock part? It's Sarah again, but surprise, she can't knock either because...you guessed it, no arms! You probably thought the joke was deep.
Thing? Person? IDEK-
Please stop repeating jokes- they're not funny if you repeat them-