Boris Karloff's voice changes when he speaks for the Grinch. Originally he spoke in his "Narrator" voice throughout. After recording was complete, the highs in his voice were mechanically removed for the Grinch, giving him the gravelly voice heard in the finished version.

Thurl Ravenscroft, who sang the song, is best known as the voice of Tony the Tiger in numerous Frosted Flakes TV commercials. Ravenscroft was picked to sing these songs because his voice was an extremely deep bass.

The lyrics to the song "Fahoo Foraze" were made to imitate classical Latin. After the special aired, the studio received letters asking for a translation from people who believed them to be real Latin.

Dr. Seuss disputed casting Boris Karloff for fear that he would make the Grinch too scary.

Though all of the production and character designs were based upon original artwork from the book, Dr. Seuss thought that the Grinch more closely resembled Chuck Jones rather than the original Grinch drawings.

Continuity

The narrator states that the Grinch was stuck in the chimney only once, yet the animation of him getting stuck in the chimney was repeated.

When the three chefs are bringing the meal to the table one of their hats keeps switching between white and blue.

When the Grinch is cutting Max's antler, the pieces that have fallen on the floor suddenly jump several inches closer to Max.

The slice of roast beast that the Grinch carves changes color as he passes it to the plate.

When the Grinch puts the antler on Max's head it has five prongs. But when Max tips forward, one of the prongs disappears as it's hidden behind his body. The Grinch only cuts off four prongs, but when Max goes upright again, the fifth prong is still gone.



Revealing mistakes

As the Grinch closes the bedroom door, the part of the coat visible between his arm and collar are left unpainted.

When the Grinch is cutting Max's antler, the cut lines appear on the prongs before he actually starts to cut.



Audio/visual unsynchronized

When the Grinch gains his strength to prevent the sleigh from falling off Mt. Crumpet, he lifts the sleigh over his head. Max the dog is left on the snow at first (when the sleigh is first raised), but then jumps up to the runner a moment later.

When Max clings to the Grinch, the Grinch lowers Max to his feet and makes him keep running. There is a sound effect when the Grinch removes his 1st foot, but not his 2nd.