Michelle Monaghan

Tom and Hannah have been platonic friends for over ten years. He's a serial dater, while she wants marriage but hasn't found Mr. Right. Just as Tom is starting to think that he has fallen in love with Hannah and is real relationship material for her, she tells him that she is engaged. When she asks Tom to be her 'maid' of honor, he reluctantly agrees just so he can attempt to stop the wedding and woo her.