Errors made by characters (possibly deliberate errors by the filmmakers): When George comes into the room when they are playing the piano he says, "Is that G stuck again?" when actually the stuck note was a C.
Continuity: When Stuart is in the sewer, he gets wet. When he climbs out of the drain, he is dry again.
Continuity: Snowbell loses his collar and tags into the lake when the Central Park altercation takes place, but he is wearing them again when he returns to the Littles' house.
Continuity: When the piano is being played, the note that gets stuck changes pitch depending on who plays it.
Continuity: At the time when Uncle Crenshaw asks for his favorite "Little" nephew at the family gathering, Grandpa Spencer is not in the group shot. After switching shots and going back to the group shot, Grandpa Spencer is there.