Things start out on a typical day in the lives of the two title characters. The Grinch, under orders from his own reflection in the mirror, is out making people's lives miserable when he suddenly crosses paths with the Cat in the Hat, who is out trying to have a picnic. The Cat unwittingly incurs the wrath of the Grinch, who then proceeds to make the Cat's day miserable by building devices with which to warp the sounds of the Cat's voice, and those of other animals, and darken the Cat's surroundings. The Cat grows upset with the Grinch's hijinks and tries to figure out how to put a stop to it all.
This was the final Dr. Seuss television special to be produced by De Patie Freleng Enterprises, shortly before they became Marvel Productions Ltd. and the second-to-last produced during Seuss's lifetime.
Tropes:
- Always Chaotic Evil: The Grinch's reflection urges him to recite an oath that, apparently, all Grinches need to keep in mind. Said oath is basically this trope.Grinch's Oath: "A Grinch is unhelpful, unfriendly, unkind; with ungracious thoughts in an unhealthy mind. A Grinch is uncheerful, uncouth, and unclean. Now say this together! I'm frightfully mean! My eyes are both shifty. My fingers are thrifty. My mouth will not smile - not half of an inch! I'm a Grinch. I am a Grinch. I'm a Grinch!"
- Animation Bump: The animation isn't quite up to where it was in How the Grinch Stole Christmas, but it's significantly better than the very cheap-looking animation that made up most of Halloween Is Grinch Night and about on par with the first Cat in the Hat animated special.
- Similar to how Chuck Jones added his own recognizable charm to the first special, Friz Freleng's influence is very obvious in some parts of the animation.
- Berserk Button: The Grinch doesn't take kindly to being called "Mr. Greenface".
- Book Ends: The special starts with the Grinch talking to his reflection who reminds him to be his mean Grinchy self. At the end of the special when he turns back to good, his reflection tries to make him mean again, only to be stopped by Max using the Vacusound Sweeper.
- Bowdlerise: Some VHS releases cut out the second half of the car chase.
- By the Lights of Their Eyes: The Grinch's Yellow Eyes of Sneakiness light up in the balcony door after messing up the Cat's Self-Soothing Song with the Vacusound Sweeper.
- Card-Carrying Villain: After a look in the mirror, the Grinch is very adamant in proving how Grinch-like he is.
- Casting a Shadow: The Grinch makes a darkhouse to cast darkness on the Cat.Grinch: A lighthouse makes light, so just for a lark, I built me a darkhouse. A darkhouse makes dark.
- Chekhov's Gun: The picture of The Grinch's mother seen near the start might seem like a throwaway gag at first, but it ultimately turns out to be an important plot point.
- Cool Car: The Grinch's car. The Cat in the Hat also drives one.
- The Conscience: The Grinch's mother; her reflection appears just in time to get him to clean up his act.
- The Corrupter: The Grinch's reflection.
- Crossover: Of two of Dr. Seuss' most iconic works.
- Disney Acid Sequence: The Grinch inflicts one of these on the Cat and the other patrons of the restaurant he is visiting.
- Does This Remind You of Anything?: After using the Vacusound Sweeper on the Cat, the Grinch tells him, "From now on, you will hear what I want you to hear."
- Even Bad Men Love Their Mamas: How The Cat ultimately foils The Grinch.
- Evil Brit: Bob Holt gives the Grinch a deep, sophisticated English voice.
- Evil Is Petty: The Grinch obsessively harasses the Cat in the Hat the entire cartoon for blocking his car and calling him "Mr. Greenface". Justified, as that is just the thing to prove how Grinch-like he is.
- Evil Laugh: The Grinch pulls one as he torments the Cat on several occasions.
- Fantastic Racism: "Mr. Green Face" could be considered a racist comment.
- Faux Affably Evil: The Grinch rather cordially presents to the Cat in the Hat his device with which he intends to relentlessly torment the Cat for the rest of the cartoon.
- Foreshadowing: During the Cat in the Hat's imaginary psychoanalysis of The Grinch, said villain has a startled reaction when the Cat mentions the Grinch's mother. Reawakening the real Grinch's memories of his mother turns out to be the key to making him good (again).
- Freudian Excuse: While imaginarily psychoanalyzing the Grinch, the Cat thinks he has one of these. Whether or not the Grinch actually has one is left ambiguous.
- Gassholes: Thanks to the Vacusound Sweeper, the love birds (actual birds) become this.Grinch: [singing] And as for your love birds, I can't stand their chirping. So I just push my button—your love birds start burping!
- Gratuitous German: The Grinch taunts the Cat, after using the darkhouse on the latter, "Are you feeling pretty gut, Mister Cat in the Hut?"
- Heel–Face Revolving Door: The Grinch starts out just as pleasant as he was at the end of his original appearance, but one conversation with his reflection in the mirror turns him evil again. The Cat manages to redeem him again and when his reflection tries to talk him back into evil, The Grinch (or more specifically, Max) more or less tells him where to stick it.
- Hollywood Darkness: When the Grinch turns on his "Darkhouse", the darkness it creates is such that the Cat "can't see my mitten in front of my face", yet the audience can still see what's happening.
- Innocently Insensitive: The Cat in the Hat probably didn't mean anything bad when he called the Grinch Mr. Greenface, but it pressed the Grinch's Berserk Button.
- Irony: After undergoing a Heel–Face Turn, the Grinch (though it's actually his dog Max) uses the Vacusound Sweeper on his reflection.
- List Song: The "Psychiatry Song" has the Cat list various incidents with the Grinch as he tries to rehabilitate him during the imaginary psychiatry session.
- Lost My Appetite: Happens to the Cat, after the Grinch uses his device on the Cat's order at the restaurant.
- The Man in the Mirror Talks Back: He corrupts the Grinch, though a reflection of the Grinch's mother appears in the end to redeem him.
- Manly Tears: The Grinch as a result of the Cat's moving song.
- Oh, Crap!:
- Max is utterly worried when he sees the Grinch revert to his mean ways by his reflection.
- When the Cat sees the Grinch mess up everything with his Vacusound Sweeper and construct the darkhouse, he is completely shocked.
- O.O.C. Is Serious Business: It is rather odd (even by Dr. Seuss's standards) to see the Cat in the Hat getting angry at the Grinch, even going as far as to call him a psychopath (a word that you normally wouldn't expect from Dr. Seuss).
- Person as Verb: Apparently "Grinches" is a verb now.
- The Pollyanna: The Cat in the Hat, as always. He does get exceptionally frustrated from having to put up with the Grinch's nastiness, but his kind and empathetic approach prevails.
- Protagonist Title: With both protagonists!
- Public Domain Soundtrack: The restaurant scene features Antonín Dvořák's "Humoresque Opus 101 No. 7", followed by Jazz and Dixieland arrangements of it.
- Red Oni, Blue Oni: The Cat and The Grinch, respectively. The former is friendly and fun-loving while the latter is melancholy and intelligent.
- Self-Soothing Song: "Relaxification", sung by the Cat as he calms down after returning home from his first encounter with the Grinch. It gets rudely interrupted by the Vacusound Sweeper messing up one of the lines.
- Troll: How the Grinch ultimately acts, particularly while operating his machine to torment the Cat.
- Villain Decay: Whereas previously the Grinch tried to ruin the holiday season for everyone and then terrify everyone with freaky monsters, here he is little more than a Troll (see above). Justified, as he had only just reverted to his wicked ways at the beginning of this special.
- Villain Song: The Grinch gets two original ones - "The Master of Everyone's Ears" and "This is the Liggle-Gear".
