Continuity mistake: In the confrontation scene where all of Mary's admirers are forcing her to choose between them, Woogie is sat on the couch with a pile of Mary's shoes. Every time the camera shoots back to him, you will notice that the position of the shoes changes each time. This is also mentioned by the directors on the DVD commentary.
Continuity mistake: This is during the scene on the outside steps of Mary's office, when Mary and Ted see each other for the first time. A suit-wearing businessman comes from the left side of the screen behind Mary twice. This happens when Mary is saying "Ted? Is...Is that you?" and the camera goes back and forth between Ted and Mary.
Continuity mistake: About one hour into this movie, when Healy is playing tag with the 'Neary group people' he goes for the touch down and Warren runs after him to get the ball. As Warren first dives for the ball, you can see that he has three red tags attached to his back, in the next shot as he lands you can see that the tags have disappeared.
Continuity mistake: When Puffy the dog goes crazy, he bites Ted's neck and Ted crashes onto the counter, smashing into some wine glasses and cups. Between a closeup and a wideshot, the smashed glass that lays around Ted changes. Also in the closeup Ted is fully on the counter, yet in the wideshot he is half on the counter, with his legs hanging off of the side.
Continuity mistake: When Pat is spying on Mary, the first morning he spies on her, Mary leaves her house and walks down to a deck and she throws Herb an apple. In a wide shot, on the barrel next to Herb is a cup, yet in the following closeup a bottle of whisky appears from nowhere.
Continuity mistake: When we see the first shot of the meeting Dom is holding, you can see the meeting table with loads of sheets on it. Then it changes to a shot of Dom standing by his big pad (just before Ted runs and yells "Mary's a fox!"), and the sheets on the table have moved around and some have vanished.
Continuity mistake: There is a scene where Ted and Mary are on a date and Mary is eating corn dog. There is a cut from her holding the corn dog where she and Ted talk and she doesn't eat any of it at all. Next shot showing the corn dog however, and there is a lot less than there was a couple of seconds before.