Loading the Dishwasher

Alright, listen up, buttercup. This here joke is banking on the ol' switcheroo of meanings. "Cumming in a woman" has one very specific, adult-type meaning. Then you hit 'em with "loading the dishwasher," which sounds innocent, but in this context, it's a cheeky way of referring to the same thing. You probably haven't even loaded a dishwasher before, though, have you?