Redhead In A Fridge

Okay, listen up, buttercup. The joke is a play on words. You expect the setup "What do you call a redhead in a fridge?" to have a funny answer that describes a redhead IN a fridge. But, the punchline is that you call the redhead "Kelly", which turns the joke into a statement about someone's name. It's funny because it's unexpected and dumb, just like you.