Continuity mistake: When the family runs out of the house to go and look for Mark, Jake is riding his skateboard and rides down the path well ahead of everyone else. In the next shot, several family members run out the gate ahead of Jake, who should have been first out the gate. (01:17:30)
Continuity mistake: When Mark and Tom get off the train, Mark is wearing his hat. When the rest of the family come around the corner, he is not wearing his hat. We see it fall halfway out the pocket of his coat when he hugs Kate, but it seems he did not have enough time to take it off and put it in the pocket of his coat, especially given the fact he was using both hands to carry the box with his belongings inside. (01:21:05)
Continuity mistake: When Tom enters the train to search for Mark, it's an Amtrak passenger train but when there's an aerial view of it, it's a commuter train. (01:23:15 - 01:24:15)
Continuity mistake: When Tom goes into Shake's office to resign as coach, the position of the football in the display case behind Shake, goes from being horizontal to tilted to horizontal again, between shots. (01:24:05)
Continuity mistake: After Mark is found, he runs into Kate's arms and hugs her and her sunglasses fall off her head, but then in the very next shot they're back on her head perfectly. (01:24:50)
Other mistake: At the end of the movie, Steve Martin is walking through the field where, just minutes before, he coached his last game (he looks at the scoreboard and his wife tells their children that he went alone to the game). Well, that seems a very immaculate football field for one that just had a college game played on it. (01:28:55)
Continuity mistake: When the family runs across the football field to meet dad, ground angle shows the children running in different order both left to right and front to back than in the overhead angle. (01:29:45)
Continuity mistake: When the kids are about to put Hank's underwear in the meat bucket, Henry and Jake insert cotton-ball type things in their noses. After they do this, we see that there is still a good amount of white sticking out, but in the very next shot, there is barely any white showing.
Other mistake: At the beginning of the film, Lorraine is in the bathroom while her sister is banging on the door outside. Notice how blonde her hair is as she is applying her lip gloss. At the breakfast table a few minutes later her hair is a different type of blonde. This is because Hilary Duff wasn't available at the time of filming the beginning of the movie and her bathroom sequence had to be filmed many months after the filming for the rest of the film had been completed.
Revealing mistake: When Kate is telling the kids that their dad is quitting his job, the boy called Mike looks directly at the camera.
Continuity mistake: When they are preparing for Oprah, Kate asks Tom to help with her zipper, Tom says it's stuck. In the next scene when she's coming downstairs you can tell that there is no zipper.
Continuity mistake: When Nora is on the phone with the whole family trying to get her to babysit, Hank throws his pad of paper on to the table and the shot cuts to Nora. The shot goes back to Hank and he throws the pad of paper on the table again.
Continuity mistake: This takes place in the scene were Charlie Baker and Tom Baker are talking about Charlie missing his curfew: when Tom wakes Charlie up, notice how he is not covered up in his blanket, but in the next shot, you can see that it is over his legs, that would not be possible seeing as how Charlie was just then waking up.
Continuity mistake: As Steve Martin is ripping out pages in the phone book about babysitting services, if you look closely, you can see that it is the same page over and over again just shot at different angles.
Continuity mistake: When the dad first gets into the bouncy castle to get his daughter, you notice him fall forward but then half a second later, he is standing up as if nothing happened.
Visible crew/equipment: When the kids are being punished by Tom for soaking Hank's underwear in meat, you can see a bit of the microphone from the overhead shot at the top of the screen. (DVD)
Other mistake: There are four days when Jake, Mark, Kim, Jessica and Mike are shown going to school in Chicago. All five wear the exact same clothes on the first three days, only on the fourth day are they dressed differently.
Other mistake: When Kate is telling the kids that their father is losing his job, Jake Baker is seen in the foreground, but in the next shot Sarah Baker is forward and Jake is behind.
Continuity mistake: When Beans, the frog, is just sitting on the pebbles and Mark is going, "Are you all right?", the the pebbles are bunched up on one end of the aquarium. But, in the shot where Mark goes back to his room AFTER Beans dies, the pebbles are bunched up on the other side.
Other mistake: When Jessica and Kim come down the stairs and Jessica is explaining what happened to Kim with Nigel and the dart, Kim looks at the camera.
Answer: Because he needed a way to coach the team while also watching his kids.