Well, isn't this a pleasant surprise! A woman came forward to Life and Style Magazine confessing that she approached Vince Vaughn and asked for a night alone with her sister. Bold and honest... ok.

He said no and really wasn't very interested in the whole concept. I guess she felt the need to share her story.

"My sister dared me to ask him to have a threesome with us. She bet me $20. "On the dance floor, we made eye contact, and I pinched his butt. When he turned around, I said, ‘I just wanted to say you’re hilarious!’ He looked surprised and said, ‘You don’t think that’s been used on me before?’" And Suzi had no more luck when she approached Vaughn later: "I said, ‘You seemed interested in me and my sister. I want to invite you to a threesome at the Roosevelt hotel with us. "He said, ‘No, honey, that won’t be happening tonight.’"
http://imnotobsessed.com/2008/05/15/vince-vaughn-says-no-to-threesome