The Grinch directing his dog, Max (Kelley), before stealing Christmas, is a result of Jim Carrey making fun of producer and director Ron Howard, imitating his style of directing. Howard found the scene hilarious and decided to include it in the movie.
According to Rick Baker, the prosthetic makeup Jim Carrey wore took about two hours to apply and one hour to remove. Carrey revealed on The Graham Norton Show (2007) that he felt so confined and uncomfortable in the latex skin that he sought counseling from a CIA agent who taught him torture-resistance techniques.
Producer and director Ron Howard was so thankful for Jim Carrey putting up with the uncomfortable hours to apply his makeup that during filming he put on the Grinch suit with full makeup and directed one day with the suit on. He intended this to be a show of appreciation to Carrey. However, when Carrey saw Howard in full Grinch outfit, he was angered, believing it was a stunt double who "looked nothing like him".
The jewels in Martha May's hair when she is explaining the Grinch's backstory is from the tree topper that the young Grinch made for Martha, implying that she still has feelings for him.
Sloane Momsen: The Who girl who dreamed of sugar plums which were literally stolen by the Grinch during the montage of him robbing all the presents in Whoville she is the younger sister of Taylor Momsen.