He got in a dog fight with some buddies and won!!!
Or he lost, depending how you look at it. Either way he's going home with the ugliest chick in the bar. It's an assumption, I know but I find it hard to believe he could find someone uglier.
He is smiling because he doesnt know that his gf actually knows he is out with a hooker.. Yea he wont be smiling for long.. esp when the itching starts