Wow, that sounds like a Brady Bunch plot. Except nobody really gets their feelings hurt and everyone laughs at the end.
Wow, that's really bad - and not just a five minute joke, but an entire week? Betray his trust, now whenever a girl likes him he will always question. Sometimes expect some news that ruins his good time. An no, he will most likely never be the same.
I would say, nothing, leave him alone. If he was my friend I would say he should never have anything to do with you ever again.
Sorry, but that was a really cruel mean joke that went on way too long. Sounds like he deserves nicer people in his life.