Warning: All spoilers will be unmarked.
Times where somebody was revealed to be a Canon Character All Along in Literature.
- Castle in the Air by Diana Wynne Jones is a sequel to her novel Howl's Moving Castle. Initially it appears to be an unrelated story set in a different part of the same fantasy world, with all-new characters. However, late in the book it's revealed that several of the supporting cast are actually characters from the first book, who've been transformed and/or enchanted by djinn magic. Furthermore, the titular castles of both books are one and the same.
- Towards the end of Danganronpa Zero, it turns out that the protagonist and original character Ryoko Otonashi is actually the amnesiac Big Bad of the franchise, Junko Enoshima.
- The main antagonist of Shin-ya Goikeda's Devil May Cry novel is a mysterious and heavily-bandaged mercenary named Gilver. It isn't until the end of the book that he's revealed to be Dante's evil twin brother Vergil.
- Older Than Steam example is in Don Quixote. The second part of the book introduces a minor character called Maese Pedro, a master puppeteer whom we think is one of the many side characters we encounter along the way. Then we find out that it's actually Gines de Pasamonte, the same con-man who handed Don Quixote his major defeat in Part I.
- The Dragaera novel The Baron of Magister Valley is a Whole-Plot Reference retelling of The Count of Monte Cristo. However, the very end of the novel reveals that Eremit, the Dantes/Count equivalent, is the same person as the Affably Evil crime lord in the Vlad Taltos books who calls himself Daifan or The Demon.
- Several in Heartless (2016) — a prequel to Alice's Adventures in Wonderland, which may or may not be a Reveal depending on your familiarity with the source material: Mary Ann is the same Mary Ann that serves as a maid to the White Rabbit, Margaret Mearle becomes the Duchess, and Raven becomes the Queen of Hearts' executioner.
- In the Horus Heresy novel Prospero Burns, one of the main characters is a Space Wolf Astartes by the name of Bear, who serves as a guide to the protagonist Kasper Hawser. Bear seems to be an original character until the very end of the novel, where it turns out that the entire time Hawser has been unconsciously translating his name from Fenrisian into Gothic. Bear's actual name is Bjorn, revealing him to be the future Space Wolves Dreadnought and hero Bjorn the Fell-Handed from Warhammer 40,000.
- The Laundry Files, as things get more serious, has started to have actual Cthulhu Mythos entities take the stage, in two cases under initially less-threatening identities.
- The entity in Mo's violin is actually a fragment of The King in Yellow.
- Mind-controlling supervillain Fabian Everyman a.k.a. the Mandate is none other than Nyarlathotep.
- The master of the Black Chamber is Cthulhu.
- Then there's the "unicorn" from "Equoid," which is strongly, strongly hinted to be an avatar of Shub-Niggurath.
- Miskatonic University - Elder Gods 101: Dean Ward is actually Charles Dexter Ward from The Case of Charles Dexter Ward.
- Outlaws Shadow features several original characters to fill out Robin Hood’s Evil Counterpart Guy of Gisbourne’s surrounding cast, but two of them are tricks pulled on Guy and the audience: the Merry Men’s Master Swordsman Finch Fitzwalter is actually Maid Marian, and Friar Tuck’s goofy and seemingly French companion Dismas is actually Robin Hood.
- Radio Silence reveals that the protagonist, Frances, was actually a background character in a Doctor Who costume that the protagonist of Solitaire, Alice Oseman's first novel, meets at a party.
- In A Study in Emerald, the protagonists initially seem like lawyer-friendly expies of Sherlock Holmes and John Watson. Their names aren't explicitly said and their backgrounds are kept rather vague. The ending reveals the real reason for this: They're not expies of Holmes and Watson, or even the real deal. They're James Moriarty and Sebastian Moran. The real Holmes and Watson are the "killers" (actually freedom fighters) that the detectives are investigating.
- Jane Yolen's Arthurian novel Sword of the Rightful King includes a character named Gawen who comes to Cadbury and gets a job as Merlinnus' assistant. He winds up getting as much focus as the canonical characters before the end, when we find out that he is actually a crossdressing Guinevere.
- Tortall Universe: In The Numair Chronicles, the gladiator slave Musenda Ogunsanwo is eventually revealed to be "Sarge", who was first introduced as a free man at a much later point in his life in The Immortals. However, this is only a surprise to people who didn't read the Dramatis Personae of Trickster's Choice, in which he makes a brief cameo; or A Spy's Guide, which has a file on him.
