There is an interview with John Stamos in Jane Magazine. One of the questions was "What's the worst you've ever screwed someone over?"
I was on the road years ago, I think it was before the Beach Boys [John played drums with the band in the mid-'80s]. I was playing somewhere in Finland, and there was a girl hanging around who was really drunk and interested in me. I wasn't into her, but my friend was. So the girl came back to my hotel, and I turned the lights down and we started making out. I said "Hold on a second, I've gotta go brush my teeth." It was dark, I left the room, and I sent in my friend, who looked like me. And she thought she was having sex with me, but she was really having sex with my friend. I was young and didn't have a conscience.