Captain Jack Harkness: Event: Ding-Dong!
Some people might not think of interrupting someone's coffee as coitus interruptus. They're the people who drink scalded coffees from coffee chains, or guzzle down instant brews just for the caffeine buzz, or maybe even grind their own coffee at home— but they aren't drinking Ianto Jones Coffee. And when someone, Jack for instance, is busily enjoying a mug of it, just about moaning over the perfection, he is really looking to enjoy it to completion.
What he definitely isn't looking for is someone at the door before he can reach a nice coffee-drinking peak. It interrupts the wonder of the coffee, and so when he goes to the door, he's very displeased indeed at the... coffee-us interruptus. Whatever. It's displeasing, whatever it's called. "What do you want?"