"Earring" joke

This man is at work one day when he notices that his male co- worker is wearing an earring. This man knows his co-worker to be a normally conservative fellow, and is curious about his sudden change in "fashion sense."
"Yo, Bob, I didn't know you were into earrings."
"Oh, yeah, sure," says Bob sheepishly.
"Really? How long have you been wearing one?"
"Ever since my wife found it in our bed."