Collective Identity

I Am Spartacus - as a lifestyle. The inverse of the classical Secret Identity. Rather than one character with multiple identities, sometimes authors will flip this around and have multiple people with one identity.

The common prank pulled by twins is a variation on this trope.

Warning: given the nature of this article, spoilers abound.

Contrast Secret Identity and Two Aliases One Character. Legacy Character is a more-specific related trope, where the identity is passed on from person to person. Identity Impersonator is when a second person temporarily adopts the identity in order to have Secret Identity and Public Identity appear together. Also loosely related to Dead Person Impersonation.

Anime and Manga

 * Zero from Code Geass ends up sort of like this towards the end. Sort of. To clarify, CC once dresses up as Zero so Lelouch may escape the army, and at the end of the series
 * Also utilized early in the second season.
 * Ghost in The Shell Stand Alone Complex; the nature of a Stand Alone Complex permits like-minded individuals to independently function as an autonomous collective, as was the case with the Laughing Man and the Individual Eleven.
 * Magical Girl Lyrical Nanoha As has the masked Mysterious Protector, who is revealed to be.
 * In Bakuman｡, in a similar example to that of Fujiko Fujio up ahead, the Ashirogi Muto moniker is shared between Mashiro and Akito; in this case, the idea is to avoid comments from envious people at their school like it happened late in junior high.

Comic Books

 * The Marvel Comics character The Scourge of the Underworld was an entire conspiracy collectively posing as a single vigilante killer.
 * Scrier, a player in the Spider-Man Clone Saga turned out to be played by an entire mystical cult.
 * The Shadow first takes on the identity of Lamont Cranston when he is out of the country, but when the real Lamont turns up, he and the Shadow both use his identity, allowing the Shadow to be seen in one place and Lamont in another.
 * DC Universe
 * Trident, an opponent of the New Teen Titans, was actually three separate individuals masquerading as a single villain.
 * Similarly, the Crimson Fox of Justice League Europe was actually a pair of twin sisters sharing both a single heroic and civilian identity (after having faked the death of one sister).
 * In The Killing Joke, the costumed villain Red Hood is actually just a mask which the members of a robbery gang take turns wearing, the better to confuse the police. (At least, if the flashback scenes are to be believed.)
 * Ladyhawke, ally of Spider Girl, is actually a pair of twins masquerading as an indefatigable superheroine who seems to be in two places at once.
 * In Tangent Comics, an alternate world series, was three different people. You don't learn this until  second appearance.

Film

 * The Ghostface killer in the Scream series was more than one person.
 * In some of the novels, Bernardo also wears the Zorro costume in order to distract and mislead pursuers.
 * Bernardo Has also been known to play the part of Zorro to divert suspicion from Diego while he has an alibi (Such as being imprisoned or questioned on suspicion of being Zorro)
 * Zorro's friend and sometimes love interest/accomplice Lolita Pulido has also donned the mask
 * in Zorro the Gay Blade Don Diego and his brother Ramon both are Zorro.
 * The Mask of Zorro, Anthony Hopkins plays the original Zorro (Don Diego de la Vega) and Anthony Banderas is his trainee, Alejandro.
 * The brief Tv Series Zorro and Son was actually about an older Don Diego training his son, Don Carlos, to take his place.
 * The big twist in The Prestige is that
 * Hot Fuzz:
 * The Dread Pirate Roberts

Literature

 * The Opera Ghost in Maskerade is multiple people. ("You recognize him because he's wearing a mask? Think about what you're saying!")
 * In Ben Bova's novel The Multiple Man is actually a set of seven cloned siblings
 * Murder on the Orient Express by Agatha Christie.
 * in Bimbos of the Death Sun.

Live Action TV

 * Used in one episode of Jonathan Creek where the mention of a character being leads Creek to realise that there are two men with one identity, the logical inverse of.
 * In Human Target, it turns out that Chance's name isn't Chance: the identity of Christopher Chance has been handed down for years.
 * The four brothers in Himitsu no Hanazono work together as the mangaka Yuriko Hanazono.

Professional Wrestling

 * The Bella twins started in the WWE as just Brie Bella, who would be losing a match, then duck under the ring where her twin sister Nicole would be waiting to beat down the heel and take the victory as Brie. Strangely enough (or maybe not because...it's Professional Wrestling) they were treated as a Face not a Heel even though they were obviously cheating. Once they were "outed" as being really two people they became Tag Team Twins.

Tabletop Games

 * Forgotten Realms being Gambit Pileup setting, it's no wonder there were such cases as team Xulla.
 * In Warhammer 40000, many members of the Alpha Legion use the name of their Primarch, Alpharius, instead of their own. Some of them even undergo surgery and psychological indoctrination to more closely resemble him.
 * In the Horus Heresy novel Legion Alpharius

Theater

 * The Importance of Being Earnest: Both Jack and Algernon use the alias Earnest Worthing. Each proposes while using this identity and Hilarity Ensues when Earnest's two fiancees meet each other.

Video Games

 * The Gray Fox in The Elder Scrolls Oblivion. He is thought to be immortal, but in fact is a succession of master thieves wearing the same magical mask.
 * In Ace Attorney Investigations At the end of the game
 * In one of the three Special Episodes of Pokémon Mystery Dungeon: Explorers of Sky Sunflora must go on a mission to capture an outlaw, a Haunter who is said to be invincible. She eventually discovers
 * In Umineko no Naku Koro Ni, Beatrice and especially Clair have a lot of this going on. Some of it is Legacy Character-based. Other aspects are less so. By the end of the game, there have been at least twelve or so different characters who could lay claim to being Beatrice in some way.
 * In Warnings at Waverly Academy, twin sisters share an identity so they can both attend the exclusive school which only one of them could actually register for.
 * The Black Raven from Professor Layton and The Last Specter is actually.

Webcomics

 * In the world of the webcomic A Modest Destiny the superhero Crimson Blade is actually an identity that's shared by several hundred people. This discovery terrifies the vampire Lord Fluffy.

Western Animation
"Two-Face: The way I figure it, Gordon's got a bunch of them stashed someplace, like a SWAT team. He wants you think it's one guy, but...
 * In the Batman the Animated Series spin-off movie Mystery Of The Batwoman, is actually three different people.
 * During "Almost Got 'Im", the villains swap their ideas about who Batman really is while playing poker. This is Two-Face's suggestion.

Joker: Oh, you're always seeing double."


 * In an old Bugs Bunny cartoon, Tortoise Beats Hare, Bugs is wondering how it could be possible for the Tortoise to beat the Hare in Aesop's fables. As The Other Wiki puts it, 'Bugs is left wondering if he's been tricked; then all ten turtles approach and reply, "Hmmm...eh, it's a possibility!"'
 * Tex Avery, director of the above, used the same gag for the Droopy cartoon Northwest Hounded Police. And in the first Screwy Squirrel short, it is revealed at the end that there were two Screwys (and two dogs as well).
 * My Little Pony Friendship Is Magic:
 * And in "Ponyville Confidential", Apple Bloom, Scootaloo, and Sweetie Belle work for the school's newspaper as its gossip columnist, "Gabby Gums".

Real Life

 * The respective authors of Hardy Boys (Franklin W. Dixon) and Nancy Drew (Carolyn Keene) are not a single person. The series are "ghostwritten," with different authors using the same House Pseudonym.
 * Fujiko Fujio, The manga artist responsible of Doraemon and similar works, is actually two people: Hiroshi Fujimoto and Motō Abiko. When the collaboration broke up in 1987, each artist continues to use the Fujiko Fujio moniker, but adds an identifier to avoid confusion -- Fujiko F. Fujio (Fujimoto), and Fujiko Fujio (A) (Abiko).
 * Sci Fi author Jack McKinney, most well-known for the Novelizations of Robotech, was a pen name for the team of James Luceno and Brian Daley. (After Daley's death, Luceno wrote a few novels solo as McKinney.)
 * They call themselves Anonymous. They are hackers on steroids, treating the web like a real-life video game. Sacking websites, invading My Space accounts, disrupting innocent people’s lives - and if you fight back, watch out.
 * *van explodes*
 * Nicolas Bourbaki, the greatest French mathematician who never existed.
 * Occasionally, the inker for a comic will be listed as M. Hands or a variant. This is a shorthand for "Many Hands", used when multiple inkers are required for a rush-job and none of them want the credit.
 * Red Dwarf is the work of Grant Naylor - that is, Rob Grant and Doug Naylor.