Factual error: In the bowling alley scene, Jack's friend tells him that Kate is well-liked in all of Union County, but in the movie, Jack and Kate live in Teaneck, which is in Bergen County.
Continuity mistake: When Jack is watching CNBC the bottle of Yoohoo changes position when he yells "thats my deal" and then it changes back again.
Visible crew/equipment: In the scene when Jack and his friends are at the bowling alley, Jack bowls down the aisle. When the bowling ball is just about to hit the ten pins you can see a reflection of the camera filming the scene in the shining bowling ball.
Factual error: The movie, set in December 2000, depicted Christmas Eve as a weekday although it was actually Sunday.
Continuity mistake: In the bowling alley scene when Jack is talking to his best friend Arnie about the Fidelity Bank and Trust things move around on the table top. In one view Arnie's beer and glove are touching. The camera cuts to Jack and then back to Arnie where the glove and beer are now inches apart.
Revealing mistake: In the bowling alley scene where Jeremy and Nick are discussing the red-haired woman, you can see Nick shaking from laughter and even hear it. It is easier to spot if you have watched the outtakes. Nick simply could not contain his laughter during this scene and so they just shot him from behind and left it in. This happens in another scene as well, when they first enter Jeremy's "manly" den. These two were just having too much fun filming this movie. Watch the outtakes.
Continuity mistake: After Jack makes the chocolate milk for his daughter, the size of her milk mustache changes back and forth in the following shots.
Continuity mistake: When Jack is changing the baby's diaper, a package of diapers appears on the table.