Sherlock was slumped in his chair idly plucking the strings of his violin when John came in. With a thoughtful look, John leant down and sniffed Sherlock's hair.
"I was just thinking how we've begun to smell alike."
"Well, that was inevitable."
"What do you mean, inevitable?"
"When two people have exchanged as many bodily fluids as we have, it is inevitable that we should begin to share some bacteria, and it is bacteria breaking down the body that causes odors," observed Sherlock absently.
"Want to exchange some more?"
"Oh, God, yes! I thought you'd never ask."