In this year's triptych of terror, Homer is the cheery, yet homicidal "Fat in the Hat" in the Dr. Seuss parody, "Oh, The Places You'll D'oh!", Bart and Lisa are forced to share a body after Bart (literally) loses his head in "Dead and Shoulders," and in "Freaks No Geeks," Homer is a circus strongman who convinces his trapeze artist fiancee Marguerite (Marge) to seduce a sideshow freak (Moe) and steal his prized emerald ring.
Treehouse of Horror XXIV contains examples of:
- Action Survivor: Bart in the opening navigates his skateboard around various monsters and chaos to make it home.
- Adaptational Heroism: Marguerite in "Freaks No Geeks" is depicted as genuinely sweet and kind and not willingly involved in Homer's plot to kill Moe. In the original film, Cleo actively conspires with Hercules to poison Hans.
- Adaptational Villainy: The Cat in the Hat was a chaotic being, but certainly not a murderer. Because this is a Halloween special, however, the Fat in the Hat beats up children and adults alike, robs Apu at gunpoint, and will kill people.
- Alice Allusion: Lisa in the opening; she falls down the rabbit hole and finds herself in Alice's pretty blue dress. It segues into a reference to Pan's Labyrinth shortly afterward though.
- Avoid the Dreaded G Rating: Inverted. The Bloodless Carnage in this installment were of ways that the writers got sick and tired of the TV-14 rating on the THOH installments that were rated before and since.
- Ax-Crazy: The Fat in the Hat.
- Body Horror: Bart's situation while he's attached to Lisa's (and later Selma's) shoulder. Played for Laughs when Bart ends up on Selma's body and the two of them end up in "Freaks No Geeks" as part of the sideshow.
- Bloodless Carnage: Bart being decapitated, then Lisa, in "Dead and Shoulders."
- Call-Back: Bart's head on Selma's body is reused in "Freaks No Geeks" as a member of Burnsum and Bailey's Freak Show. Even Burnsum refers to him/her as the "Terrifying Callback".
- The Cameo:
- The Hypnotoad appears in place of the toad from Pan's Labyrinth in the opening sequence.
- Kang and Kodos make their usual cameos as two of Burnsum's freaks.
- The Cat Came Back: Played for Drama; the Simpsons kids escape from the Fat in the Hat and head home, only to find he's already inside. Fittingly, the Fat in the Hat is a parody of the Cat in the Hat.
- Continuity Nod: As Lisa leaves the school there are framed photos of characters and moments from past Treehouse of Horrors, namely Homer being tortured by the Raven from I, alien maggie from IX, Dr Hibbert and the various human/animal hybrids from XIII, and the Grand Pumpkin from XIX.
- Eaten Alive: Milhouse, Lard Lad, and Smithers in the intro
- Enfant Terrible: During the opening, Maggie drives a black car and forces Milhouse off a bridge to his death below. She also runs over Homer when she makes it back to the house.
- Even Evil Has Standards: The Fat in the Hat is a murderous lunatic, but the idea of having Mike Myersnote play him in a movie adaptation is, to him, worse than going to Hell.
- Everyone Has Standards: The kids run away from the Fat in the Hat when they realize that he's completely unreasonable and an outright murderer. Though they do wait until he gets them candy.
- Eyes Do Not Belong There: Mr. Burns as The Pale Man.
- The Faceless: Marge in "Oh, The Places You'll D'oh!", is shown only from the neck down as a reference to the original The Cat in The Hat book.
- Fate Worse than Death: The Fat in the Hat spares Apu after holding him at gunpoint, deciding that forcing him to spend time with Manjula and the Octuplets is a much worse fate.
- Faux Horrific: Burnsum introduces one of the freaks as the most frightening creature ever seen. It turns out to be just plain old Moe, looking and acting no different than he usually does. And yet the audience gasps and screams in utter horror.Moe: So, uh, anyone here from New Jersey? (Woman raises her hand) Ah, I'm going there next week. (Woman screams and faints)
- Funny Background Event: In "Dead and Shoulders," while Bart is flying his kite, Milhouse becomes allergic to a flower and is carted off by paramedics.
- How Dad Met Mom: "Freaks No Geeks" turns out to be this in a Shout-Out to the Framing Device used in How I Met Your Mother.
- Humans Are the Real Monsters: Most likely the reason why the Universal Horrors are chasing after the people of Springfield while wielding Torches and Pitchforks.
- Hypnotize the Captive: The Hypnotoad briefly does this to Lisa in the opening.
- Impaled with Extreme Prejudice: Maggie stops The Fat in the Hat from hurting her and her siblings by impaling him with the very umbrella he used to mug/murder people.
- I Gave My Word: For all his horrific deeds, the Fat in the Hat does honor his promise to get the kids some Halloween candy after curing them of mumps. He does so by robbing Apu.
- Karmic Death:
- During The Fat in the Hat's mayhem, he kills and skins Moe's character. Using his own umbrella against him, he's skinned by the Simpson kids and shown as a new rug on their floor.
- Jimbo, Dolph, and Kearney try to sneak into Burnsum's tent without paying. A lion emerges and spits out some of their clothing.
- Kick the Dog: Throughout the special with The Fat in the Hat's rampage, Strongman and Burnsum's bad treatments of the freaks, and Maggie and Mr. Burns as the Pale Man in the intro (although that last case is a Foregone Conclusion if you've seen the movie).
- Murder the Hypotenuse: Homer the Strongman intends to kill Moe after he's married Marge/Marguerite so he can claim Moe's emerald wedding ring and pawn it for a supposed better life. Played with, as it's shown that he doesn't really care about Marguerite but treats her a lot like a trophy wife.
- Noodle Incident: How did Dr. Nick get his head sewn onto Dr. Hibbert's body?
- Off with His Head!:
- Bart is decapitated and has to have his head sewn onto Lisa's body to survive. By the end, they both get their heads cut off by a sawmill and are attached to Selma and Krusty.
- Lenny is unintentionally decapitated by Carl (as Blade) as he charges after mutated Homer in the opening. He proceeds to pour his coffee down his exposed esophagus.
- Ralph also has his head knocked off by the severed Jebediah Springfield statue head. He is still able to lick his ice cream.
- Reference Overdosed: Del Toro fit as many sci-fi and horror references into the opening as he possibly could.
- Many legends of the genre appear, such as Stephen King scrawling "All work and no play makes Jack a dull boy" on the walls of Bart's classroom, Alfred Hitchcock sits next to Krabappel-and then causes some birds to attack her, Ray Bradbury tattooing a muscular man ("The Illustrated Man"), Richard Matheson (who wrote "I Am Legend") shaking his head in disapproval at Bradbury's tattoo work-and one of the novel's vampires standing next to him, Edgar Allan Poe lets a raven land on his arm, and H. P. Lovecraft having tea with one of Cthulhu's tentacles.
- Of course, Del Toro fits in Shout Outs to his entire filmography up to and including Pacific Rim: Cronos (the device is on the cash register), Mimic (Marge as a Judas Breed), The Devil's Backbone (Homer as Santi at the couch), Blade II (Homer as a Reaper up until the couch and Carl as Blade), Hellboy (2004) (Groundskeeper Willie as Hellboy fighting Kroenen), Pan's Labyrinth (Mr. Burns as the Pale Man, and Bart as the Faun and Lisa as Ofelia in the ending sequence) and Pacific Rim (Gipsy Danger fights Knifehead in the background of the town battle.)
- Four incarnations of The Phantom of the Opera (specifically the the novel, the 1925, the 1943, and the 1962 versions) appear at Lisa's rehearsal, and the teacher is dressed as the Phantom of the Paradise.
- The Universal Horror versions of Dracula, Frankenstein's Monster, Wolfman, Mummy, Gilman, Bride of Frankenstein, the Metaluna Mutant, and the Invisible Man form a mob to chase the Springfield residents.
- The Zombie Apocalypse at the power plant could reference any zombie film, but is probably specially calling to mind Night of the Living Dead (1968).
- The Cyclops version of Wiggum that eats Lard Lad is from The 7th Voyage of Sinbad
- Maggie drives The Car to run over Millhouse.
- As noted above, at the couch Lisa wears Alice's dress while falling down the rabbit hole, and upon landing sees the Hypnotaod.
- Under the earth, we see the dead bodies of the original versions of the Simpsons and the skeleton of Godzilla.
- The pan across Springfield includes: Rod Serling, the Robot from Lost in Space, the Man in the Beaver Hat from London After Midnight, a Xenomorph, the Ymir, one of The Mole People, the skeleton soldiers from 1963's Jason and the Argonauts, the creature from The Thing from Another World, a Morlock, Ro-Man, Cavor's craft from The First Men in the Moon, Count Orlok, aliens from Invasion of the Saucer Men, the Fly, Klaatu's spaceship and the robot Gort, two of the 'freaks' from Freaks, and Rondo Hatton from House of Horrors (1946).
- Rhymes on a Dime: A given in the Seussian "Oh, The Places You'll D'oh!"
- Shout-Out: In "Oh the Places You'll D'oh," Maggie is modeled after Cindy Lou Who as she appeared in the iconic Chuck Jones adaptation of How the Grinch Stole Christmas!.
- Selma with Bart's head attached sing the first four lines of James Taylor and Carly Simon's "Mockingbird".
- "Freaks No Geeks" ends with an out-of-nowhere nod to How I Met Your Mother.
- "Oh, The Places You'll D'oh!" is packed with Dr. Seuss references — apart from the obvious Whole-Plot Reference to The Cat in the Hat and the title reference to Oh, The Places You'll Go!, there are references to, among other things, The Lorax (the Borax, who "plastered [his] likeness on CON-sumer goods"), How the Grinch Stole Christmas! (the character designs of Maggie and, arguably Moe; Burns calling the Fat "a son of a Grinch"; the scene in the homeless shelter), Yertle the Turtle (the turtle stack shown outside the Simpson house), The Sneetches (Flanders as a Sneetch with a cross on his belly), The 500 Hats of Bartholomew Cubbins (Bartholomew and his hats are shown outside Moe's), What Was I Scared Of? (the walking pants), Green Eggs and Ham (the eponymous dish is shown in Moe's pickle jar), Horton Hatches the Egg (Horton is seen drinking with his trunk at Moe's), songs sung by a mixed chorus in the style of the vocal songs from the Dr. Seuss animated TV specials of The '70s, and many others.
- Sir-Not-Appearing-On-This-Poster: Aside from one promotional shot of the Simpson children in typical Seussian fashions, "Oh, The Places You'll D'oh!" and its characters (such as The Fat in the Hat) are noticeably absent from promotional materials.
- That includes The Simpsons: Tapped Out, which had a splash screen showing tombstones, one of which read "The Fat in the Hat Quests". Sure enough, that was the Seuss parody's only mention in the game.
- Slasher Smile: The Fat in the Hat and Stephen King in the opening
- Stealth Pun: Smithers (a closeted gay man) as a fairynote to Pale Man Mr. Burns in the opening.
- Subverted Rhyme Every Occasion: The Fat in the Hat is Killed Mid-Sentence just short of finishing a verse.Fat in the Hat: I’m staying forever, you’re all stuck with that! ‘Cause I’m your new daddy, the Fat in the- OW!
- Take That!: The Fat in the Hat trashes The Borax for selling out, referencing the film adaptation's Misaimed Marketing (in particular, the infamous Lorax Mazda commercial). Also before dying, The Fat in the Hat states he'll tolerate hellfire, but not a movie adaptation with his character played by Mike Myers. Ironically, Dan Castellaneta voiced Thing 1 and Thing 2 in said movie.
- Tar and Feathers: Strongman's fate in "Freaks No Geeks", which turns him into the "World's Strongest Duck"
- Tempting Fate: Marge in "Oh, The Places You'll D'oh!" is sure she's the only one wearing a Catwoman costume for Halloween. The next scene shows several other people wearing Catwoman costumes. Including Comic Book Guy, who apparently didn't realize it was Halloween.
- Tongue Trauma: Strongman is able to lift things with his tongue. It's stretched out in comedic fashion, with the hint that it is quite uncomfortable.
- Too Dumb to Live:
- Bart gets decapitated when he ties the string to his box kite around his throat. Even worse, he's flying this kite around an airport.
- Homer mistaking sleeping pills for yogurt mix-ins.
- Toon Physics: Bart survives being decapitated, yet Skinner and Homer got decapitated in Treehouse of Horror XX and it was realistically depicted.
- Torches and Pitchforks: Seen in the opening, but with a twist; they are wielded by the classic Universal monsters as they pursue the mortals.
- Visual Pun: One of the posters of the freak show shows "The Spineless man." Which shows a picture of Skinner literally crooked for not having a spine, who is also the character that can't stand up to anyone.
- Whole-Plot Reference: Dr. Seuss works (particularly The Cat in the Hat) and Freaks
- You Monster!: When Strongman outright states his intentions, Marguerite responds that while Moe may be ugly on the outside, Strongman is the real monster on the inside.