Continuity mistake: When Bonnie pulls away from her house in the taxi to go to New York, there are no pedestrians on the other side of the street. In the next shot, just a moment later, two people are standing on the previously empty sidewalk facing the departing taxi. (00:43:50)
Continuity mistake: When Mark is walking down the hallway on his first day of school, he runs into two bullies. After the bully grabs Mark's glasses he then pulls Mark's hat down. Then, when the other bully is about to pull Mark's hat down the hat is up and perfectly fine. (00:45:25)
Continuity mistake: When Charlie is doing his homework, he throws his pen on the book on his bed and looks at the picture of his girlfriend. He then picks his pen up from the book in his lap. (00:53:35)
Continuity mistake: When Tom is in an office at the Stallions, Charlie comes in and he says "Dad we need to talk" and then he picks up a rugby ball with one hand. In the following closeup though he suddenly is holding it with both hands. (00:53:35)
Continuity mistake: When Tom picks the kids up from school, Mark hands his dad a picture. In a closeup Mark is holding the piece of paper at the top, yet in the wideshot he is holding it at the side. (00:54:30)
Continuity mistake: At school Mike Baker knocks the latte out of the bullys hand, and the latte falls to the floor spilling a bit of drink on the bullys shoe. Yet in the next wideshot of Mike lunging at the bullys legs, the drink cup has vanished and both of the bullys shoes are clean. (00:58:55)
Continuity mistake: After the scene where the kids get grounded, there is a scene of Mark laying in bed. He then rolls over in bed and stares at a picture of him and his mum. In front of the picture are his glasses, but in the very first overhead shot of Mark laying in bed, the glasses weren't in front of the picture. (01:01:00)
Continuity mistake: At the hospital, Dylan has a black eye and broken arm after Tom fell on him at his birthday party. A little later when Kate goes to the Shenk's house to tell them Mark has run away, Dylan shows no signs of the injuries he suffered. (01:04:45 - 01:18:25)
Continuity mistake: When Tom and the family are getting ready for Oprah to come round, Tom is on the phone to Kate and he runs over to a vase of yellow flowers and nearly knocks them to the ground. Between shots the way he touchs the flowers changes. (01:08:50)
Continuity mistake: When Hank and Nora come to visit, Hank is walking on the sidewalk leading to the house, and we see him take off one of his gloves. In the next shot, he takes off the same glove. (01:10:00)
Continuity mistake: When Mark spills water on Tom, Tom has a big wet patch on his trouser leg. This disappears when he goes upstairs. (01:13:20)
Continuity mistake: When Nora and Hank are standing by the bainster, when the whole family is fighting, in one shot Nora's arms are down by her side, but in the next shot, her hand is up by her chest. (01:15:35)
Continuity mistake: When Bonnie Hunt announces that Mark has run away, she has no paper in her hand. It cuts to Steve Martin, then back to Bonnie who now has Mark's note against her chest. (01:17:05)
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)
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.
Answer: Because he needed a way to coach the team while also watching his kids.