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.
Continuity mistake: When the Baker's first move in and Dylan's family comes to visit, right after Dylan falls off of the Chandelier, Jake throws one of his shoes down (not both). In the next shot, the father is holding both shoes.
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.
Other mistake: When Steve Martin is seated at the table trying to find a babysitter, there are several quick shots of the phone book as he crosses out numbers, turns the page, etc. The very last shot of the phone book is backwards! While its easy to see the phone book, if you zoom in on the shot, you can clearly see that the tiles, words and letters on the board partially obscured by the phone book are backwards too.
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.
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.
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: In the kitchen when Kyle and Nigel run to their dad, Tom, and start yelling and doing macho actions, in a wideshot you see Charlie walk from the stove, over to the worktop where Henry, Kim and Jessica are making sandwiches and he puts something on a shelf. Then in the following closeup of Nigel and Kyle you can see in the background that he has instantly vanished.
Continuity mistake: At the beginning of the movie, Steve Martin comes into their bedroom after a jog where his wife is proofing her manuscript. There's a pinwheel type of decoration attached to the lamp on top of some family photos in the corner by the window. In the 1st shots, you can even see its shadow on the lamp. Steve says (to Bonnie Hunt) "We could use a little change around here - like this lumpy old mattress." He then moves to the mattress facing her and the photos are still there but the pinwheel thingy is gone.