Accidental Pervert: The title character at one point winds up flying face-first into the bosom of his childhood crush. Without removing his head from her chest, he greets her with the muffled words, "Hello, Martha."
Adaptation Expansion: The movie expands on the Grinch's character, actually creating legitimate motivation for his actions and a reason why he stole Christmas this year as opposed to any previous year, in comparison to the original story where he simply hated Christmas and randomly decided that after 53 years of putting up with it, he would ruin it.
Affectionate Parody: A subversion of sorts. The Grinch starts to realize he's speaking in rhyme at certain points, and goes out of his way to try and prevent it. He does, however, keep going just before his Heel-Face Turn. At the very least, it's in character for him in the beginning.
Age Lift: Cindy Lou Who was "no more than two" in the original. Her age isn't specified in the film, but six-year-old Taylor Momsen is obviously not two.
Batman Gambit: Unlike the book and the cartoon, the Grinch's plan hinging on Christmas being ruined by him stealing the presents actually holds merit as the Whovians truly are that materialistic. And it works!
Spanner in the Works: What ruins the plan? Mayor Augustus blaming Cindy Lou for the disaster. If he hadn't, her father wouldn't have defended her and, thus, realize what the true meaning of Christmas was.
Berserk Button: The Grinch actually starts to enjoy being involved in the Christmas celebrations... until he opens his gift to find an electric razor, a bad joke that triggers his deep-seated childhood rage, increased when Augustus proposes to Martha right in front of him.
The Grinch does this in reverse to the Whos, sending unpleasant mail to random destinations in the post office: "Jury duty! Jury duty! Jury duty! Blackmail! Pink slip! Chain letter! Eviction notice! Jury duty!"
He flips through the town phone book at random, loudly voicing his displeasure with each name he reads. "Hate, hate, hatehatehatehate, double-hate, LOATHE ENTIRELY!!"
Blatant Lies: The Grinch. "Look, I don't want to make waves, but..."
Also Mayor Augustus: "Martha was my girlfriend..."
Plus the whole thing with Cindy Lou Who and the Christmas tree.
Breath Weapon: While wandering Whoville incognito, The Grinch knocks out a pushy hat salesman with his foul breath.
Brick Joke: After he finishes pranking the Whos, he goes back to his lair and states that his heart size has gone "Down a size and a half!", meaning it's three and a half sizes too small. Near the end, his heart grows three sizes, leaving it still a half size too small. It explains his remaining Jerk Ass tendencies. And Martha May Whovier wouldn't have it any other way.
The Grinch: Who wants the gizzard!?
Who: I do!
The Grinch: Too late! That'll be mine...
Broken Aesop: The backstory presented in the film makes it clear that the Grinch's hatred of the Who's way of celebrating Christmas is perfectly justified, yet the end is still presented as him needing to learn a lesson. To be fair, the Who's end up learning the same lesson too.
Christmas Carolers: The one thing the Grinch hates most of all is when all the Whos down in Whoville gather together, and start caroling around the Christmas tree. There's a song on the subject by Ben Folds called "Lonely Christmas Eve".
Crapsaccharine World: A light example. While Whoville seems like a festive, friendly place at first, the Grinch - and Cindy Lou - feel that the Whos are very materialistic about Christmas. Not to mention how The Grinch was treated when he was a kid.
Subverted with the Grinch who didn't win Martha over as a child.
Easily Forgiven: While more cynical towards the Grinch in this interpretation, you have to give credit that the Whos are willing to give him a chance twice over after completely destroying the festivities:
The Grinch: I am the Grinch that stole Christmas... and I'm sorry. *beat* Aren't you going to cuff me? Put me in a chokehold? Blind me with pepper spray?
Mayor Augustus Maywho: You heard him, Officer. He admitted it. I'd go with the pepper spray.
Officer Wholihan: Yes, I heard him all right. He said he was sorry.
Enormous Engagement Ring: The ring offered to Martha May Whovier by Mayor Augustus Maywho is visibly large. It's also hideously gaudy.
Even Evil Has Standards: While the Grinch is not above destroying anything Christmas related, he avoids running women pushing children on the stroller even if the end result ends with his (stolen) car exploding. He'll cause a little chaos and mayhem, but he avoids people getting hurt. After Max gets the Grinch's attention that Cindy's in real danger from the machinery, he reluctantly saves her.
Jerkass Has a Point: The Grinch calls out the Whos for being so greedy and demanding on Christmas. Even though he hates Christmas, he makes sure to point out what he sees in them.
Jerk with a Heart of Gold: The Grinch, after discovering the meaning of Christmas. He's still kind of a jerkass, but he's considerably more affable. His heart is still a half-size too small, and Martha probably wouldn't have it any other way.
Large Ham: Jim Carrey really packs on the ham as the Grinch.
"Hello, little girl... HOW DARE YOU ENTER THE GRRRRRINCH'SLAIAH!!!! THE IMPUDENCE!! THE AU-DACITY! THE AHN-MIDDEHGATED GULL!!! You called down the thunder now, get rrready for the BOOOM!!! Gaze into the face of fe-ahhh!"
The Whobiliation scene qualifies by the moment the Grinch gets the razor as a gift.
Morality Pet: A literal version! Max doesn't let the Grinch leave the Post Office without saving Cindy Lou.
Murder the Hypotenuse: While not actually involving literal murder, Augustus Maywho tries to get rid of the Grinch and the Grinch takes extra care in ruining Maywho's life when terrorizing the Whos.
My Master, Right or Wrong: Max the Dog seems to be this, following the Grinch faithfully whether his intentions are good or bad. Almost like a... well, a dog.
Mythology Gag: The opening shot depicting Whoville as being inside a snowflake is a shout out to Horton Hears a Who!, where Whoville is located in a similarly microscopic speck of dust.
Fridge Brilliance! Who's to say that it's not the same speck, but stuck on a snowflake? It would explain why Whoville can have both warm and snowy weather. Plus in Seussical, the Grinch makes a cameo in the speck of dust Horton finds.
Many designs (including but not limited to the clouds over Whoville) are based on swirls and spirals, echoing design elements in the original book.
Papa Wolf: Cindy Lou's father, despite being a timid man, stands up for her when the Mayor blames her for the Grinch's thievery. In fact, he's the one who makes those in Whoville realize the true meaning of Christmas.
Also, despite being visibly scared, he steps in front of a crashing sleigh to stop it because his daughter's on board.
Paper-Thin Disguise: This ugly cave creature puts on a red coat and Santa hat. Boom! He automatically looks "just like Saint Nick."
Partially justified as a way of keeping people from noticing him from a distance (i.e. "a figure on the roof tops in a Santa's hat on Christmas eve must be Santa!") When Cindy Lou approaches him, he tries to keep the tree between them to help keep her from seeing him properly.
Pyro Maniac: The Grinch, burning down the Whos' Christmas tree.
Quote-to-Quote Combat: After Cindy Lou nominates the Grinch to be the Holiday Cheermeister, both she and the Mayor take turns quoting from the Book of Who to argue their positions. The Mayor loses badly.
Grinch: That's what it's all about, isn't it? That's what it's always been about! Gifts, gifts, giftsgiftsgiftsgiftsgiftsgifts! You wanna know what happens to your gifts? They all come to me. In your garbage. You see what I'm saying? In your garbage! I could hang myself with all the bad Christmas neckties I found at the dump. And the avarice. The avarice never ends! "I want golf clubs!" "I want diamonds!" "I want a pony so I can ride it twice, get bored with it and sell it to make glue!" Look, I don't wanna make waves, but this whole Christmas season is stupid!Stupid!Stupid! There is, however, one teeny-tiny Christmas tradition that I find quite... meaningful. Mistletoe. Now pucker up and kiss it, Whoville!
Saving Christmas: Inverted; in fact, the inversion of this trope is the premise of the story. Then it's played straight when the Grinch Saves Christmas from himself at the end.
In a sense, his stealing of Christmas is what ended up saving it for the Whos, as it helped them to realize what was truly important about Christmas.
A news story about the Grinch being spotted in Whoville is accompanied by a photo of him striding like Bigfoot does in the famous Patterson-Gimlin film.
Shrunken Organ: The Grinch's heart. Starts as two sizes too small before going down "a size and a half". It grows three sizes, meaning it is still a half size too small. It shows.
Shut Up, Hannibal!: Just while the mayor blames Cindy for letting the Grinch ruin Christmas, her dad says "If she's not [glad], then I am. I'm glad he took the presents." Then he proceeds to smack an awesome lesson onto him and the citizens, saying that gifts and contests weren't all that defines Christmas.
Up to Eleven: Inverted in the beginning as the Grinch's heart is two sizes smaller than what a normal one should be. And then shrinks another size and a half. And then grows three sizes, but unlike the book, this still leaves it a bit on the small side.
V8 Engine Noises: While all Who cars seem to have tiny engines with, like, one cylinder, the small car the Grinch hijacks from a couple of small Whos sounds like it has a V8 under the hood (or grows one as soon as he guns the engine).