If you look closely, you can see a little Grinch statue in Clause's lair scenes.
The entire script was written in 1 day.
There are subtle jokes that point back to "How the Grinch Stole Christmas" (2000).
The last scene of the film is loosely based off of the "Oh, The Whomanity!" scene in "How the Grinch Stole Christmas".
Max is based on Max the Dog from "How the Grinch Stole Christmas" (2000).