In the beginning of the movie, Mike pulls into Chris' driveway and you see his "so cool" license plate on the back of his car. Towards the end of the movie when they see his car at the French restaurant, it's on the front of the car...you can see the front headlights to verify it.
This isn't a slip-up. This movie takes place in Chicago. In Illinois, vehicles are required to have a front and back license plate. Both plates are going to say the same thing. It's an honest mistake though, since some states only require a back license plate.