Dad: Why did Jimmy fall off his bicycle?
Son: Why?
Dad: Because somebody threw a washing machine at him.
Dad: Why did Jimmy fall off his bicycle?
Son: Why?
Dad: Because somebody threw a washing machine at him.
Alright, listen up, buttercup. The joke is funny 'cause it's unexpected and absurd. You think Jimmy fell off his bike 'cause he's clumsy or somethin', but BAM! Washing machine! It's so random, it's hilarious. You probably fall off your bike all the time, don't you?