In the theatrical trailer, a scene which is not included in the DVD is shown with Franck telling George and Brian that there will be "sterks" (storks) at the baby shower. During the Scrabble scene, you can see "sterks" on the board, along with the other pregnancy-related words.
The set used for the interior of the Banks' home had to be rebuilt from scratch for the sequel. With no presumption of a sequel during production of the original movie, the set was destroyed after production completed. Set crew had to recreate the entirety of the set based only on a few remnant sketches of the original set, and had to infer most measurements based on the known sizes of various reference items in the original film.
Annie's shoes change from Reeboks to plain white shoes and back to Reeboks between shots in the basketball montage even though it is supposed to be the same game she is playing.
At the end when Matty is handed his new nephew, his hand position changes from the time he gets it and everybody yells "two hands!" to when the camera angle changes an he turns away.
Nina supposedly went into labor and delivered her baby a month early but when George is holding Megan in the hospital she is a large, plump baby. A baby born a month premature would not be that big.