Halloween is Grinch Night (Or It's a Grinch Night or simply Grinch Night) was a television special and the second appearance of the Grinch and the third appearance of Whoville. It premieried in 1977 and won an Emmy. However it has several issues that pit it and it's supposed sequel the Grinch Grinches the Cat in the Hat in error with the first two.
For starters, the Grinch is a villain in Grinch Night with a desire to have a "Grinch Night Ball" around Whoville due to his annoyance with sounds during the Sour Sweet Grinch Night wind. This makes the Who's afraid for some reason and we are never really told why that is or why the Grinch now decides to hurt Whoville when ieleven years ago he supposedly became nice. Second, at the end Max gives the Boston Cheer to his master and runs off with the protagonist, Euchariah, who we will get to in a bit, yet he is with himin The Grinch Grinches the Cat in the Hat, Both of these facts have caused issues with Seuss historians who can't really put this in either prequel or sequel status.
Next is the cast. Cindy Lou Who is not seen in this installment with the Grinch, though two characters resembling older versions of her do appear(There namesare Obediah and Mithiah). The main protagonist is a boy named Euchariah. Euchariah is a really unique character that Seuss wrote. Unlike the other two main children of Whoville that being Cindy and Jojo from Horton hears a Who Euchariah does not need someone to find him in an aprtment building to save the town or to be fooled by a costume and not realize the danger he is in. In fact as he stares the Grinch down over a battle of wits Euchariah "Show Your Spooks! I Will not Flinch!" To which he is submitted to horrors that had TV guides advising parents not to let children under the age of eight watch the program.
There is another issue here that also deals with Euchariah and his two siblings: They look like actual people, cartoons yes, but they do look like actual human beings. This too has raised issues with Seuss historians as they do not look like the animlas of Horton hears a Who or have attenas and tails like How the Grinch stole Christmas.
This has given folks saying that maybe the two Whovilles in Seussdom are separate places and that the one on the dust speck is a difrrent breed of animal then the one that concerns the Grinch. In The Lorax special, a mountain similar to the one in Grinch Night appears and that special is set in supposed real life.