I would LOVE to be walked in on while some dude's dick is up my ass. Preferably by someone I don't know, but still. I've had an unintended audience for blowing a guy before. Resulted in blowing two extra guys.
Takes me back to catching my mate getting fucked by his older brother, in their hotel room, when a group of us went to Spain, the brother was supposed to keep us all out of trouble, not a chance, he was crazier than all of us put together