Two Aliases, One Character

There are two characters. Maybe one is never seen, or is only mentioned in passing, or whose face is never seen, or it's a book and the author ain't much for descriptions. These two never meet, are never in the same scene, and/or never interact with the same characters. Eventually it's revealed that they're actually the same person. Note that, contrary to what the trope name suggests, they do not actually need two aliases (i.e. pseudonyms) for this trope to apply - but either the characters in-universe or the reader/viewer (or both) need to believe them to be separate people, until The Reveal.

This trope also applies to Multiple Personalities, so long as characters/audience are unaware that they physically share the same body. It is possible to use this as Character Development if the character assume(s/d) a new alias unbeknownest to other characters, especially if the previous alias and persona are considered dead or status unknown.

This is often a source of Wild Mass Guessing, with fans trying to argue that two different characters are really the same person, usually with no given reason why this person would have another identity.

Contrast Collective Identity, which is Two Characters, One Alias.

Anime And Manga

 * L in Death Note isn't just one of the top 3 detectives in the world, he's all of them under separate aliases.
 * Also, early in the series the audience never sees Light's father around the house, being told that he's working. Turns out it's the police chief that's already been around a few chapters.
 * Later example: After Light assumes control of the Kira Taskforce and presents himself to police around the world under the name "L" while still maintaining his identity as Kira.
 * Masquerade/ in Bakugan.
 * Fullmetal Alchemist:.
 * In a couple of arcs of Higurashi no Naku Koro ni, combines this with  and Mind Screw.
 * In Baccano!'s Drugs and the Dominoes, Claire Stanfield not only has the reputation as the world's most violent and dangerous assassin, but is also the greatest challenger to that claim, . Gustavo then makes the mistake of hiring the latter to kill the former (along with his stepbrothers, the Gandors) and violent Hilarity Ensues.
 * Misao Amano/Pixy Misa in Magical Project S.
 * Used, and taken to its illogical presumptions, in Umineko no Naku Koro ni. Many theories imply that one person is impersonating/trading places with five different members of the family and the servants and an Unreliable Narrator keeps the personas separate. And everyone else is just being paid off.

Comic Books

 * Double Helix in Wild Cards, who is a shapeshifter.
 * The entire team of Thunderbolts in their first run.
 * Silverhawk, where the actual identity of the hero was kept secret from the reader for a full year of the comic's run
 * in both the original Astro Boy and Naoki Urasawa's retelling Pluto. (In the former, just a disguise; in the latter, an alternate personality.)
 * In Watchmen,
 * Star Wars Legacy brings us Morrigan Corde and . It's unclear which one came first, or if they're aliases of a third identity.
 * /Red She-Hulk in Incredible Hulk. Also /Red Hulk.
 * In an early issue of Justice League of America Year One, each of the five superheroes makes an acquaintance in their civilian identities - Perez the coast guard stands up for Aquaman in a bar, Lora Denton investigates Hal Jordan's test flight for the FAA, Officer Sherman looks in on Diana Lance's flower shop, Detective Jackson starts working with forensics officer Barry Allen, and supercop John Jones is approached by reporter Cal Redmond and creepy fellow detective Vince Logan. It turns out all of these

Film

 * Keyser Soze/ in The Usual Suspects
 * Darth Vader/Anakin Skywalker
 * Chancellor Palpatine/Darth Sidious, if you watch the movies in chronological rather than production order.
 * League of Extraordinary Gentlemen. The British Government official known as "M" who brought the League together turns out to also be . And then it's revealed that his real identity is.
 * In Scott Pilgrim vs. the World,.
 * In Tron: Legacy Castor, Zuse's gatekeeper, actually is Zuse.
 * Also inverted and subverted. Clu allows Sam to believe he's Kevin, but by the time he reveals otherwise, Sam's in the process of working it out. Sam pulls this on top of the Encom tower, when he reveals to the security guard that he is Kevin's son, and as such is in charge of the company. Then he jumps.

Literature

 * The Strange Case of Doctor Jekyll and Mr. Hyde. Originally, it was a big twist to discover at the end that Jekyll and Hyde were the same person.
 * Chetter Hummin/Eto Demerzel/ of the Foundation series.
 * Preem Palver, farmer/
 * The first Foundation one is also a pun
 * Scylla/ in Marathon Man. The novel makes a big secret out of it.
 * In Agatha Christie's Murder on the Orient Express, is actually  . This is, to the best of my recollection, not foreshadowed in any way.
 * Another Christie: in One, Two, Buckle My Shoe,  This is convoluted even by Christie standards.
 * The Westing Game: the entire point of the game is that
 * The Scarlet Pimpernel
 * Fight Club: Tyler and . In fact, at one point, the narrator even wonders if Tyler and are the same person, invoking this trope.
 * In Dragaera . In this case, the two characters share some common friends, but The Reveal is totally a shock because they seemingly have little in common, although once the reveal is made, clues in earlier books become noticeable.
 * In Gates of Ivory, Gates of Horn, by Tom McGrath,
 * are both aliases of in American Gods by Neil Gaiman.
 * The twist endings in two novels of The Culture, The Player of Games as well as Surface Detail both make use of this trope.
 * In the .hack// prequel novel AI Buster, turn out to be the same guy. The franchise does this a lot, actually, made easier by the characters' use of online aliases.
 * In Angels & Demons and The Da Vinci Code, the mysterious unseen leader of the villains turns out to be a seemingly sympathetic character. It's also done slightly differently in Digital Fortress. Dan Brown seems to love this trope.
 * In 'The Girl Who Circumnavigated Fairyland In A Ship Of Her Own Making', the lost Good Queen Mallow is now.
 * In Vampire of the Mists, and  are revealed at the end to be the same person.
 * Both the eponymous schemer of The Count of Monte Cristo and the philanthropic Lord Wilmore are aliases of the same character: Edmond Dantes.
 * and  in The Midnight Folk by John Masefield.
 * 'The Last of the Venitars' takes this to the extreme.
 * Aragorn as Strider/Thorongil/whatever name he uses for adventuring and Aragorn as Elessar the Isildur's Heir in Lord of the Rings. There's no surprise for the reader, but in-universe not many people know they are the same person. Barliman Butterbur particularly is very surprised when he learns that the King who Returned and Strider the strange vagabond he knew are one and the same.

Live Action TV

 * Lost:  and  were the one and the same, and in addition equal to.
 * Don't forget Locke's dad, who went by many names, including.
 * Life On Mars: The Morton Brothers/.
 * Tin Man had a mild example when the party went to find "The Seeker" in the realm of the unwanted, who could guide them to Ahamo, one of the Queen's helpers. Well, yes, they are the same fellow...and that same fellow's third alias was the Queen's consort (and DG & Azkedellia's father).
 * Power Rangers:
 * Power Rangers in Space: Astronema/.
 * Power Rangers Wild Force: Master Org/.
 * Power Rangers Dino Thunder: Mesogog/ and Elsa/Principal Randall.
 * Power Rangers Mystic Force: Koragg/.
 * Power Rangers Jungle Fury: R.J./.
 * Power Rangers RPM: Tenaya 7/.

Theatre

 * from The Umbilical Brothers.

Video Games
": [in Raven's voice] *sighs* Guess you can't fool the nose of a dog..."
 * In the third Sly Cooper game,.
 * in Disgaea.
 * Manhunt 2 has.
 * In Tales of Vesperia, it is revealed that.
 * BioShock (series) has
 * In Mitsumete Knight, the enemy Generals love to pull this : Salishuan the Spy is  ; Zeelbis the Bloody is   ; and Wolfgario the Ravager is.
 * Xenogears: The mysterious guy in the red gear who calls himself Id turns out to be
 * The Origami Killer in Heavy Rain is.
 * Devil May Cry 3 reveals.
 * The Raincoat Killer in Deadly Premonition is.
 * At the very end of Ghost Trick, it is revealed that Ray is.
 * In Tales of Vesperia, it's pretty damn obvious that Raven is hiding something. Cue jaw-drop from everyone as  reveals himself to the party for the first time, and Repede, who hates everyone, actually welcomes him. And then...


 * The World Ends With You has the Composer being.

Western Animation

 * Zuko/Blue Spirit from Avatar: The Last Airbender.
 * Robin/Red X in Teen Titans.
 * In earlier episodes; but then Red X becomes a sort of Enemy Without with no real explanation as to whom the new Red X is.
 * There are two villains in the 2003 version of Teenage Mutant Ninja Turtles: The Shredder and Ch'rell. Guess what is the result?
 * In DuckTales episode "The Masked Mallard", there is the titular character of the episode gone rogue and a reporter named Lawrence Loudmouth bad mouthing him..
 * In the sixth season of South Park, we meet Lu Kim, the Chinese owner of the Asian restaurant City Wok. Nine seasons later, one episode introduced Dr. Janus, who suffers a severe case of Multiple Personality Disorder.
 * In The New Batman Adventures episode "Sins of the Father", "The Judge" is revealed to be.

Real Life

 * One of the famous Iga ninja is rumored to have done this to confuse his enemies, even going as far as having his subordinates pretend along with him (his alias was... a competing ninja leader in the same area).