Trivia: Cesar Romero refused to shave his moustache for the role of Joker, so it's still visible under his makeup.
Trivia: The iconic song, "You're a Mean One, Mr. Grinch" was sung by Thurl Ravenscroft. Mr. Ravenscroft (who died in 2005 at 91 years old) is also famous for providing the deep, resonant voice of Tony the Tiger, the brand mascot for Kellogg's Frosted Flakes.
Trivia: Just after Linus seals his letter to the Great Pumpkin in an envelope, he walks past Lucy who is sitting on the floor watching TV. In her hands, Lucy is holding an issue of TV Guide Magazine. On the cover? Lucy, sitting on the floor in the same position, wearing the same blue dress. (00:07:00)
Trivia: Fred Gwynne (Herman Munster) and Al Lewis (Grandpa/Count Dracula) worked together previously on "Car 54, Where Are You?" This is referenced playfully after Herman and Grandpa discover the secret of Munster Hall.