I go shopping. I buy a passion fruit.

When I get to the till, the cashier asks me what the passion fruit is. Thinking it'll save me some money, I tell him it's a tomato.

"Tomato my ass!" he demands. So I do. I jump over the till and thoroughly tomato his ass.

Apparently he didn't understand what he was demanding of me. That is a expression he won't use again so flippantly.