When Tom and Dylan are hanging from the chandelier, there is a shot of the ceiling showing the chandelier coming loose.
Then when it cuts back to Tom hanging from the chandelier, in the background behind him is a crewmember holding a boom mic!!!
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).
At the beginning during the breakfast scene, the eggs splatter all over everyone and some gets on Steve Martin's chin and you can see it fall off, they then show a shot of Fed Ex and then show Steve Martin again and the egg is back on his chin.
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.
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. 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.
In the sequence when Tom is on the phone trying to find a babysitter, he repeatedly says he needs a babysitter for 12 children.
However, Charlie, Lorraine and Nora, who does not even live at home, are much too old to need a babysitter.
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.