Jim Carrey met Geisel while filming “Man on the Moon” and stayed in character as Andy Kaufman the entire time.
1
Geisel also retained veto power over the film and used it to cut basically all references to anything related to adult-themed humor. Among the cuts were a stuffed Cat in the Hat hanging in the Grinch’s cave, plenty of bathroom humor, and some sexual innuendo on which Audrey wouldn't deign to elaborate.
2
One notable adult-themed bit did make it into the film, whether Audrey realized it or not: A flashback shows a holiday party where Who couples are all tossing their keys into a glass jar, implying that some Whos are swingers. Or maybe just responsible drinkers?
3
Studio executives were worried people wouldn’t recognize Jim Carrey with in all his Grinch makeup, but their fears were unfounded.
4
Carrey was so put off by his first session on the makeup chair - reportedly an 8-hour process - that he threatened to quit immediately so producer Brian Grazer brought in a man who trained CIA agents in torture endurance to give him some distraction tactics. Completely appropriate response.
5
Carrey was such a dickhead that the makeup artist doing his work was instructed to take a leave of absence to prove how important he was to the project. Carrey promised to treat people better and he returned to work.
6
The makeup ordeal was such a talking point - seriously, shut up - that Ron Howard decided to undergo the entire process. For a whole DAY. The horror!
7
Howard gave his daughter Bryce Dallas Howard a small extra part as a Who in the background. He also put his brother Clint in the film as a sidekick to the mayor.
8
According to Jeremy Howard, who played Cindy Lou Who’s brother (Drew Lou Who), two key Who characteristics got scrapped sometime between Who School and production. One was a certain way of walking, the other was an accent; Whos were originally meant to sound like they all hailed from upstate New York.
9
Max was played by 6 different shelter dogs.
10
Mariah Carey co-wrote “Where Are You, Christmas?” proving that she is truly the Christmas song queen. She was originally going to perform the tune too, but the deal fell apart for unknown reasons and Faith Hill got the call.