If you sang that along with us, then you are a Happy Endings fan and we love you. Let's hang out. If you don't know what that little song was, then you don't know Derrick. Thankfully, we can help you with that. In this exclusive extended scene from Happy Endings: The Complete First Season (out on DVD tomorrow), Penny's (Casey Wilson) at the wedding of the dude that she was supposed to marry…if she didn't find anyone better, that is. And she did what any desperate and slightly crazy girl would do…pulled a "fake fiancée."