Revealing mistake: In the scene where the Klumps go to the "All you can eat" restaurant, Sherman sits at the corner of the table next to his father. When he sits he puts his hands on the table. His father does the same, but because the actor is edited into the scene the fathers hand goes through Sherman's hand. Both hands are on the same place on the table, and you can see through them. (00:12:10)
Revealing mistake: When Grandma Klump strips down to Buddy there are several close-ups of her face, and below that you can see her neck and collar bone etc. In the close ups it is painfully obvious that this is a healthy man's body not an 80 something year old woman's. (01:49:45)
