Much like canon, Eight for the Ninth is positively filled with shout outs.
Fan Theories/Plotlines
- Izuku's notes on the resemblance between Nana and Inko, and his eventual disappointment that they are not related, refer to the usual plotline where Inko is Nana's daughter.
- Another fan plotline/theory that gets referenced as of Chapter 11 is the "Red Shoe Theory": the basis being that since Quirkless people have an extra toe joint, they have to have custom-made shoes for a proper fit - which unfortunately end up being sold in a particular shade of red as an indirect form of discrimination. This becomes a plot point with Aoyama, who is ignorant of his former Quirklessness because all of his shoes are bespoke, and thus aren't red.
- Tying into that, Chapter 29 plays into the idea that Tomura/Tenko was born Quirkless and All For One found and forced Decay on him as part of his gambit to control him. Said theory is proven to be canon with Chapter 419 of the manga.
- Another fan theory gets referenced in Chapter 16: the Second Torchbearer of One For All somehow being a time-displaced Katsuki Bakugo. While the two are Identical Strangers in canon, the fic gives the Second a sister that he says is "likely in (Bakugo's) family tree somewhere" - and who is later mentioned to have a grease-producing Quirk. Kyuseishu's Heroic Analysis eventually mentions this, as well.
- Izuku recognizing Kyudai Garaki as Dr. Tsubasa is a reference to the theory that the two are one and the same, before it was officially confirmed in canon. Tying into that is the idea that Izuku did have a Quirk and Garaki/AFO stole it when he was 4, rather than just being born naturally Quirkless.
Other My Hero Academia Fanfics
- All Might not telling Izuku his real name because he forgot is a reference to With Confidence.
- Nana's unofficial hero name being "Nimbus" is a reference to I am [REDACTED].
- Hikage's notes mention that he sometimes calls his Quirk "Super Anxiety", a reference to Danger First.
- Daigoro's joke about Izuku being mostly "anxiety and hero trivia" and the conversation about compersion come from Solidarity Among Students.
- The "Desutaru Agency" mentioned in chapter 5 is a reference to the same-named hero agency (Death Star Agency, itself a Star Wars reference) in Type-2 Hero. Bakugo's fate as of Chapter 10 of getting enrolled in Ketsubutsu's Villain Rehab program is a reference as well.
- Izuku getting out of Todoroki's glacier by breaking it up from the inside with One for All is a clear reference to Total Command.
- The same fic is also referenced with All for One's Neural Rewrite Quirk.
- Some of the new hero names come from other fanfics: Venus (Mina) was inspired by "Fight Like A girl", while Heartjack (Kyouka) and Prism (Toru) are from "Written By Heroes for Heroes".
- Tenya interning with Gran Torino was inspired by What's in a Hoard?.
- Eri describing Ochako as having "pink chipmunk cheeks" is a reference to Green Tea Rescue, where Eri identifies Ochako that way.
- The idea for Mei and Melissa becoming students for both Support and Hero Course came from Haigha.
- Nedzu's term for brutally dismembering someone is to "visit them an unpleasantness", an Unusual Euphemism coined in What it Means to Be a Hero.
- Knowing about Eri has caused Sir Nighteye to have his Quirk be interfered with, something previously seen in Flashback.
- One of the Quirks All for One has stolen is Lactic Acid Elimination.
- Another reference to What it Means to Be a Hero is All for One's Plant Hair Quirk, Photosynthethic Hair, a joke that Izuku made about his Messy Hair.
- Power Loader listing Izuku as Support equipment is a reference to Announcer AU.
Other Media
- In general, the Empathy Quirk and the bonds it forms bring to mind the Social Link/Confidant system in the Persona games.
- After Jiro and Iida lose their match against Pony and Yui in the Heroes vs Villains exercise despite far better communication, All Might paraphrases Picard's speech about how one can make no mistakes and still fail anyway.
- Pony hums We Are The Champions after winning in the battle trials.
- Yoichi makes a Star Wars reference, specifically "I have a bad feeling about this". Daigoro lampshades the remark, asking if it comes from something old.
- Star Wars also gets a reference with the Achuto Planetarium where Izuku and Ochako have their first date - Achuto coming from Ahch-To, the planet Luke was on during The Last Jedi.
- For the Joint Training work, the students go to Kuraudo Island, named after Bespin's Cloud City.
- Chapter 72 is mostly set on Mosai Ward. Mosai is a reference to Mos Eisley.
- Tomura's hometown is called "Ouen-Beru", a reference to Luke Skywalker's uncles, Owen and Beru Lars.
- The forest where Native is attacked by the Hound and Eleph High Ends is called "Iiwaku Forest Reserve", a reference to Ewoks.
- Yoichi mutters "Guess his is the drill that will pierce the heavens" when Monoma combines Shoji's Dupli-Arms with Kaibara's Drill.
- When Mina gleefully declares that she'll have to find out for herself who Izuku is dating, Daigoro remarks, "Well that's fucking ominous."
- Akira Fuki's (pompadour guy from the entrance exam) maternal grandfather is one Gentaro Kisaragi, known in this timeline as the Rocket Hero: Cosmic.
- "Well, I calculated the odds of this succeeding versus the odds that I was making a horrible mistake... And I went ahead and did it anyway."
- One of the hashtags inspired by Izuku's speech to Todoroki is #TilAllAreMight.
- Ushimitsudoki Aquarium (Gang Orca's Hero Agency) was a location in Horikoshi's previous work Omagadoki Zoo, where it served as a base for Sakamata, a villainous precursor to Gang Orca.
- Mei's dad has wild white hair and exclaims "Great Scott!" at one point - the author admits that the moment he gave the man white hair, he could only think of him as Dr Emmett Brown.
- The Hamada Enterprise Expo is a reference to Big Hero 6.
- When Mei was shocked at Izuku getting tickets to the Enterprise Expo, Izuku's response was "We have a Yaoyorozu."
- Izuku's full hero name (Ultimate Hero: Kyuseishu) is partially inspired by a certain (primarily) nine-man group of ultimate saviors.
- After Tsuyu compares Eri to a narwhal, the Vestiges wall off Yoichi because he still remembers this song
. - Re-Destro takes a page out of Yzma's book and vents his anger by smashing statues of Izuku.
- Izuku and Yui watch a movie marathon during their first date, the first movie being from Ultra Series.
- The sound that marks the forming of a Level 3 bond is VWORP!
- During the final exam, Kinoko throws soil (used to grow her mushrooms) in Aizawa's eyes while shouting "Pocket Sand!"
- Nezu states that the entire class passing is "A surprise, to be sure, but a welcome one."
- The Quirk Amplification Device created by David Shield is the practical version of a Starlin ring, named after Jim Starlin, the creator of Thanos and the Infinity Gauntlet.
- The training regimen used by Hitoshi Marubashi and Shizuku Kendai (the original bearers of Bonding and Power Stockpile, respectively), consisted of a hundred push-ups, sit-ups, and squats, and a ten-kilometer run a day, along with a hundred reps with weights and other exercises. Hitoshi is also mentioned to be going bald, though it could be attributed to the stress working as a guerrilla through the Dark Age of Quirks rather than the workout itself.
- When it turns out that Momo's connection to One for All lets her tap into the stockpile to use Creation, Yoichi jokes that she could create an unlimited amount of blades.
- After Izuku's bond with Tsuyu reaches level three, Black Whip forms a bodysuit around Izuku that Yoichi compares to Spider-Man wearing the Venom suit.
- Apparently Yoichi's last words were to tell his brother, "Your princess is in another castle."
- When class 1-A is thrown off the cliff during the summer training camp, Setsuna says "Okay, everyone who's not dead, sound off!"
- When riding a helicopter (as 1-A does to reach the Wild, Wild Pussycats' lodge), they blast Ride of the Valkyries through its speakers.
- When the League attacks, Melissa and Mei commandeer the helicopter again, this time blasting Fortunate Son.
- Yoichi keeps calling out "Kamehameha" to Izuku's new energy-shooting move. Izuku has no idea what the Hawaiian King Kamehameha has anything to do with it.
- Since he got that move from Nejire Hado, Izuku decides to name it Hadoken. Similarly, Izuku has no idea who the reference is until he plays Super Smash Bros. Eternal.
- When Class 1-B sees Izuku and the Ennead at the training camp, Awase calls bullshit. Tenya overhears and shouts, "Language!"
- Yui insists on Izuku helping come up with a "Super Sentai" Stance and Catchphrase for the Ennead. Some ideas they toss around are "Now, count up your sins!", "Where there is life, there is a roar of justice!", and "The strongest braves in history!"
- Chapter 40 is titled Welcome to the Jungle.
- The hero students steal a couple lines during the villain attack on their summer camp.
- The title for Chapter 42 is Life, the Universe, and Everything.
- The previous bearer of Izuku's copy of Super Regeneration was called Logan Wadsworth.
- The teleportation sound effect from Bonding's Level 4 is a Team Four Star reference for the noise Instant Transmission makes when used, which is a loud Pop.
- Kinoko makes a Pun about Saiko being unable to outsmart a bolete.
- Saiko Intelli canonically used a phrase reminiscent of Sento Kiryu's "The laws of victory have been decided." Here she also uses two more.
- After telling her classmates her plan to counter Fumikage, Reiko, Kinoko, and Koji, she says "Now, let's begin the scenario."
- As her classmates take their places, she crows, "Am I not great? Am I not awesome? Am I not a genius?!"
- Additionally, Saiko sifts through her memories in a manner reminiscent of Philip searching the Gaia Library.
- When they learn of the conspiracy theory videos regarding Izuku, Mina and Setsuna quote Final Fantasy VII: Machinabridged.Izuku: Can you not use that term for it?
Mina: You can't tell our murderboners what to do!
Setsuna: We are erect with rage! - The current owner/holder of Kuraudo Island is Marcus Cuvier VII, which has several references:
- Cuvier comes from George Cuvier, French naturalist that was one of the first to suggest species could go extinct. Fittingly, the Cuvier family's Quirk allows them to bring species back from extinction.
- The "VII", combined with Kuraudo/Cloud, refers to Final Fantasy VII and Cloud Strife.
- His Pro-Hero name is Jurassic Mark.
- His physical description resembles John Hammond.
- Cuvier's pet Hoplophoneus is called Nakina, an anagram of Nanaki (Red XIII's name in Japanese). This reference is furthered by the fact that she's the thirteenth descendant of the first Hoplophoneus he made.
- Cuvier's granddaughter, Susan, is named after Susan Hendrickson, the discoverer of the T-rex skeleton known as "Sue". Her Hero name is Clever Girl, from the famous Jurassic Park quote.
- Chapter 57 is titled "Everybody Walk the Dinosaur", named after the lyrics from the song of Was (Not Was).
- The main Mexican hero school is Santo Kalimán Academy. Two Mexican heroes/teachers are La Cucaracha Colorada (based on El Chapulín Colorado) and El Popo (based on Dragon Ball Z Abridged!Mr. Popo), short for Popocateptl, Mexico's largest active volcano.
- Besides a group of the Santo Kaliman Academy and UA students, a third group comes from America's Xavier's Institute, with one of the students referencing Archangel.
- Menagerie, the Arc Villain in the Dinosaur Island arc, has a Quirk based on Animorphs. He is also named Dawson Jamrach, after Charles Dawson (the man who crafted the Piltdown Man forgery) and Charles Jamrach (the owner of an exotic pet store in Victorian England).
- Adding to the Animorphs reference, his mother is revealed to be named Cassie.
- Nejire's super move against Nine is called Giga Drill Breaker.
- According to Izuku's notes on Daigoro, the first hero school in Japan was called Ishinomori Academy. Shotaro Ishinomori was the mangaka best known for being the author of Super Sentai and Kamen Rider.
- Izuku describes Lariat's fight against All for One like this: In the end, Daigoro was brave, Daigoro fought smart, Daigoro was prepared. But Daigoro still lost.
- Melissa says to Ibara: "Don't apologize for the stupid, you'll never have time to sleep."
- Yui gives Mei a scarf inspired by her favorite tokusatsu heroes. The inventor girl even wonders if she could make a baby to cause it to billow dramatically even if there wasn't any wind, much like in Kamen Rider.
- The hero Bolo is based on Robocop, with his name being an inversion of the first two syllables of his name and his hero ranking being taken from Robocop's release date, July 17, 1987.
- When Izuku is channel surfing after the Tea Spillers' reveal, he comes across a movie where a character complains about a truck trying to kill him. Another show features someone saying that if not for their horse, they wouldn't have spent a year in college.
- After Miruko attacks other heroes that were about to violently attack a crowd of peaceful protesters, Yoichi has something to say:
- Mei builds the butter robot from Rick and Morty.
- Chapter 70 is titled "I'm So Meta Even This Acronym".
- Chapter 72 is titled "Future Imperfect" named after the Star Trek: The Next Generation episode of the same name.
- Rumi's mom's name is Juri.
- Yui's Awesome Personnel Carrier is shaped like a Brachiosaurus, much like the Brachiozord from Power Rangers: Dino Thunder, except this one is made of weapons instead of Zords, the head is baton that Mt. Lady uses is similar to the one Tommy uses in the series and the tail is a whip. And in typical Power Rangers fashion, Yui finishes the fight by slashing Machia with her energy sword and turning her back on him as he explodes.
