A prank pulled on a person by placing ones finger into a sweaty butt crack and then placing said finger in an unsuspecting person's ear with a twisting motion while saying 'Moist Michael!' Similar to a wet willie.

The female version is called a Moist Michelle.
I just got Ben back for drawing on me with a Sharpie at the party the other night by giving him a 'Moist Michael'
by texas_lexus January 10, 2011