Continuity: Annie's hair when introduced to the caterer.
Continuity: George's socks change color from the supermarket to the jail scene.
Continuity: When Annie and Bryan go to change for their honeymoon, George takes a shortcut. The time it would take for them to change would be significantly longer than the time it takes George to get to the stairs via his "shortcut," though he still manages to miss their exit.
Continuity: The huge chandelier in the dining room disappears and reappears throughout the film.
Continuity: When Annie and George are talking in the back yard (after Annie announces that she is going to get married), Annie is alternately wearing a gold necklace/pearl necklace between shots.
Continuity: When Annie comes home and announces to her parents that the wedding is off, the position of the tea set items on the tray in George's hand changes between shots.
Continuity: When George is in the jail cell talking to his wife, his chin is resting on the cell bars, but only in the shots when he is facing into camera. In the reverse shots (over his shoulder) he is clearly several inches away from the bars.
Continuity: When the wedding party starts the procession down the aisle at the church, Howard (Franck's assistant) starts out having Nina and Matty proceed on their left feet. By the time the bridesmaids are proceeding down the aisle, Howard's timing is off with the foot they should be on (in other words, if you think "left-right-left-right" in time with the music, they're on the "wrong" foot, even though they're still in step with each other).
Continuity: It is made a point on the day of the wedding that George has been cheated and is wearing a blue tuxedo. However, in every scene during and after the wedding, with the exception of one, he is wearing a black tux.
Factual errors: The swans in the bath honk like geese when in fact they are silent.
Continuity: In the opening credits, the wedding invitation from Annie's wedding says that the wedding date is in October. But, when Annie and her parents are discussing the wedding with Franck, they clearly state that the wedding will take place on January 6th.
Continuity: After Annie gets home from Rome and her family is at the dinner table, the shots alternate between Annie holding her fork picking at her food when the camera is on her to her arms folded when the camera is behind her.
Revealing mistakes: When Annie puts the ring on Bryan's finger at the wedding, it is very obvious by the tan line and indention that he already has been wearing a wedding ring for a long time.
Revealing mistakes: When the two young boys were moving the cars from the street, how did they reach the pedal? They were way too small to move the cars themselves.
Errors made by characters (possibly deliberate errors by the filmmakers): When George Banks is in the supermarket complaining about the conspiracy instituted by the hot dog companies and the bun companies, he removes four buns from 3 packs of 12 hot dog buns (8 x 3=24). This would give him 24 hot dog buns. If he had simply purchased two packs of 12 buns (12 x 2=24) he would have gotten the same number of buns, without the subsequent arrest.
Revealing mistakes: When the Cops arrive to complain about the street being blocked with cars, the Police car is clearly seen in front of the house. If the street was completely blocked with the guest's cars, how did it get there?
Continuity: When the family is first meeting Frank, the candelabra in the room behind Frank is obviously lit up; however when they enter the room and sit down, the same candelabra is turned off.