In response to: What's the first thing you'd do once you came in and saw them together?
I had this happen once!
I came home and the front door was locked, but my gf's car was in the drive.
So I go in and the house is mostly quiet, which is wierd because she always left every tv on.
I head for the bedroom thinking she might be asleep and her typical sex noises from the other side of the closed bedroom door.
I get angry and burst into the room and there she is, getting after it with my BEST FRIEND!!!
I grab her clothes and throw them at her whileyelling and herding her to the front door and outside.
I go back into the bedroom and my best friend is sitting there as happy as he can be.
I look him in the eye and say...
Bad dog! BAD BAD DOG!!!