In the plane scene, the first shot shows Nadia in Doug's lap. However, in the next shot, Doug is sitting alone, and Nadia walks over and sits in his lap.
After flower girls drop petals in the church, the pattern of the flowers on the carpet changes from moment to moment.
The van carrying Doug, his best men, Nadia and the dog to the hospital after the bachelor party mishap are pulled over by a police officer. The driver of the van puts the van into reverse and smashes into the front end of the police car, causing apparent damage to the front end of the car. In the next scene, there is no damage to the police car.
In the football scene between the groomsmen and old guys; after the first touchdown, the Father-in-Law shouts "touchdown, 7 to nothing." There was no extra point attempt or field goal. It was only 6-0. However, many pickup football games count touchdowns as seven points without the extra point.