Audio problem: When Scott is making a distraction, he says, "Well, this show stinks." But his mouth is saying, "Well, this show sucks." Done in order to keep the G rating, I presume.
Audio problem: When Frost and Scott are on top of the roof, it shows the younger Scott (as seen in the first movie). Everything from movement and actors and sounds are the same, except for the way Santa yells as he falls off the roof.
Answer: David Krumholtz (Benard) is busy on his show "Numb3rs" on CBS and is committed to that so he didn't return for The Santa Clause 3. I guess they could have explained his absence, but the filmakers decided not to. They simply promoted Curtis since he was in the 2nd movie.
Carl Missouri