The Cat in the Hat (live-action)

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The Cat in the Hat is the titular protagonist of the infamous 2003 live-action film of the same name, based on the 1957 children's book by Dr. Seuss.

He was portrayed by Mike Myers, who also played Wayne Campbell from Wayne's World, both Austin Powers and Dr. Evil from the Austin Powers franchise and Shrek from the eponymous film series (all of which are much better characters/films).

Why He Fell Flat
NOTE: This will focus exclusively on the 2003 live-action film's incarnation of the character.
 * 1) He is a disgraceful and insulting representation of Dr. Seuss' well-known character of all time, as in this film he is mostly the complete opposite to how he was portrayed in the original source material; in the book and animated special, he was kind, funny, goofy, well-meaning and while he was a bit of a nuisance, he was never a legitimate threat to the kids. In the film however, he is mean, vulgar, unfunny, malicious, obnoxious and a genuinely sadistic threat to the kids.
 * 2) * In the climax, he mocks Larry for being allergic to him and then proceeds to push him off a cliff. Later on, he literally does nothing but smile when Conrad and Sally find the crate open and the latter almost gets sucked in while the former was attempting to lock the crate. To add insult to injury, when the house collapses and falls apart after Conrad locks the crate, the Cat flat-out admits that he knew everything was going to happen as he planned the whole day all along (minus chopping his tail), including almost getting Conrad and Sally killed and then getting the house destroyed, which would've also gotten both Conrad and Sally into immense trouble with their mother!
 * 3) * Also, after the house gets destroyed, the Cat offers Conrad and Sally to play a game of tennis with him in spite of their predicament and then attempts to play the victim when Conrad and Sally scold him for the house's destruction. In addition, he also lies to them that he had lost his magic hat in the nightclub earlier when he actually still had it the whole time, followed by a scene where he is also shown to be very stupid when he thought that Conrad and Sally telling him to get out of the house was a game.
 * 4) * He is also incredibly selfish as he doesn't care about anybody but himself, as evidenced in the scene where the Cat reveals that he wants to "cut his losses and ditch the kids" in one of his plans for helping Conrad and Sally, even though they would suffer at the hands of Larry. Another example of this ignorance is shown when Thing 1 and Thing 2 are messing up the house, he tells a sleeping Mrs. Kwan that he "would be furious" if it were his house.
 * 5) He says and/or does some pretty unsuitable, inappropriate and improper words/activities that are out of place for a film based on a Dr. Seuss book. Most infamously, he almost yelled "SON OF A B*TCH!" when he accidentally chopped his tail in the "Cupcake-Inator" scene, before cutting to a "HANG IN THERE BABY!" screen before he could fully say it. Yes, this is not a joke.
 * 6) * At one point during the fun song, he says, "That's why they sent him to a vet and cut off both his ba-" before changing the word to "boy".
 * 7) * He is a huge pervert, as he lusts over a picture of the protagonists' mother at one point, and in the scene where he and the kids enter a nightclub, he also lusts at Paris Hilton, who makes an out-of-place cameo in that scene.
 * 8) ** He is also technically a cat, so him lusting over the protagonists' mother and Paris Hilton, both who are humans, is considered bestiality.
 * 9) * He uses profanity-laden puns, such as when he shows his car in which he calls it the "Super Hydraulic Instantaneous Transporter" (S.H.I.T.) before he changed its name to "Super Luxurious Omnidirectional Whatchamajigger (a.k.a. the S.L.O.W.)" to prevent Conrad from saying the acronym of the previous name.
 * 10) * His infamous "Dirty hoe!" line.
 * 11) He has a very creepy makeup design compared to Jim Carrey's makeup as the Grinch, as he looks more like Pennywise/It from the titular horror film.
 * 12) * In particular, the costume design for the Cat, while somewhat faithful to the Cat's appearance in the original book, doesn’t even look like a cat; instead it looks more like a giant skunk. As the Nostalgia Critic pointed out, it's as if what happens when "Pepe Le Pew makes whoopie with Ronald McDonald."
 * 13) He has a very annoying laugh, which he uses over and over again as a cheap and poor attempt at comedy.
 * 14) He is also incredibly gross, as he often indulges in toilet-related jokes and puns (all of which are barely even funny);
 * 15) * He tells Conrad and Sally not to listen to the fish because he "drinks where he pees."
 * 16) * He, after drinking a bottle of milk, claims it's gonna "come back to haunt him" and his stomach gets big, implying the milk will give him diarrhea before burping out many hairballs.
 * 17) * He dresses up as a stereotypical redneck trucker, shows his butt and farts at the audience.
 * 18) * When the Cat has cupcake mixture on his finger, he tries to get a disgusted Sally and Conrad to eat it, implying that the Cat has a booger on his finger.
 * 19) He doesn't show any remorse or regret for all the troubles he has caused throughout the film until the end.
 * 20) Because of all these reasons as mentioned above, the Cat in the film comes off as more of a villain than a hero.
 * 21) He is the main reason why the 2003 live-action adaptation of The Cat in the Hat was very poorly received by critics and audiences alike. In fact, he and his film's failure caused Dr. Seuss' widow Audrey Geisel to permanently ban any further live-action adaptations of Dr. Seuss' works.
 * 22) He sucks at speaking in rhyme, which is unfitting, ridiculous, and of course, unacceptable since his original book counterpart could speak in rhyme.
 * 23) He often has bad eye contact with most the characters he interacts with, specifically Conrad and Sally, since most of the time he doesn't even look at the kids when talking to them, and he's more interested in telling bad jokes and winking to the camera than actually interacting with the kids.
 * 24) Overall, Mike Myers did an awful job performing the Cat and was seriously miscast as him.
 * 25) * It also doesn't help that he only starred in the film because he was legally and contractually obligated to do so by Universal executives who sued him for backing out of a proposed film adaptation of his Saturday Night Live sketch Sprockets.
 * 26) It takes his biggest problem from Season 2 of The Wubbulous World of Dr. Seuss (not acting like his book counterpart) and makes it even worse.

Redeeming Qualities

 * 1) He at least got some bits of karma when he got hit on the crotch, followed by the scene where the kids scolded him for his actions.
 * 2) He was a much better character in the book series and at least he did redeem himself near the end by completely fixing his mess in the house using a cleaning machine before Conrad and Sally's mother got home.
 * 3) He can be a bit funny in a few scenes, such as the Cupcake-Inator scene and his line "Honey, it was ruined when she bought it".
 * 4) He actually does rhyme a few times.
 * 5) The Cat's actions towards Conrad and Sally are somewhat justified if you hang on to the theory that he was just a well-meaning mentor who was helping them understand their limits about having fun, knowing that the destruction he was causing would help them learn their lessons and become better children.
 * 6) In the video game based off of the movie, he's significantly less annoying, and is more tolerable.

Trivia

 * The Cat later became the subject of Internet memes - a notable example of such a meme would be the scene of him holding a baseball bat.
 * Mike Myers recently admitted to hating the movie and regretted playing the role in said film.