This is one reason why I love my friends, their willingness to share these kinds of stories:
Last night in Manhattan:
Guy gives a cab driver a 5 dollar tip on a $4.60 cab ride........As they get out of the cab:
Girl: "Do you realize you just gave that guy like a 110% tip?"
Guy: "Oh, shit, I did? Oh, wait, yeah I did! Oh shit, damn it!"
Girl: "That's ok. It'll make up for the huge fart I just left in his cab."