Schrödinger's Player Character

Congratulations! You just bought a new RPG! The game offers three characters to play as: Alice the Mage, Bob the Fighter, and Charles the Thief! Each character comes with a complete biography in the manual, and the character selection screen, on top of explaining their stats, gives each character his unique motivations answering The Call. Alice wants to save her son. Bob wants To Be a Master, and Charles seeks to avenge his Doomed Hometown.

So you decide to pick Bob. And as you play the game, you begin wondering... What happened to Alice and Charles? You keep playing the game, reaching 100% Completion, and you never see either. Looks like Alice, Bob and Charles are Schrodinger's Player Characters. In more generalized explanation: You are given a choice of characters, and once chosen, the game seems to go based on the assumption the selected character is the only one who exists. This trope is very common in games that give you a choice of pre-generated Player Characters, so much that it may come as a surprise when it is averted and the PCs you did not choose turn up as NPCs. This can also be confusing when each character is given a different backstory. Did those events even occur?

The question is then: do the other characters exist? If not, then why not? If so, then are they the Heroes Of Another Story?

Often accompanied by Story Overwrite; if the selectable characters are stated to normally work as a team, chances are that cutscenes or the canon of later games in the series will depict them all working together, even if only the chosen character is ever present in gameplay.

Named, of course, after Schrödinger's Cat.

Action Game

 * Averted and lampshaded in Monster Racers. You choose between a girl lead or a guy lead at the start. The one you didn't pick appears and mentions they could have been you.

Adventure Game

 * In Maniac Mansion, you have the task of breaking into a mansion and saving Dave's girlfriend, Sandy. At the beginning of the game, you pick two teenagers out of six to assist Dave. The manual indicates that he only called two friends, either due to time constraints, or because he felt a smaller team would go unnoticed.

Beat'Em Up

 * Particularly common in Beat'Em Up games, where a player is offered a choice of (usually three) characters and never see the others despite the fact that the plot has them fighting together for the same objective.
 * Final Fight only allowed up to two players simultaneously, meaning that at least one of the three main characters will always be left out of the action. This is particularly egregious in the SNES version, which was single-player only and came in two versions: one that that featured Cody and a second version which replaced him with Guy (providing the explanation that Cody is still training under Guy's sensei in Japan and couldn't return to Metro City on time). The opening intro in Final Fight 2 for the SNES establishes that all three of them fought the Mad Gear gang together, despite the fact that neither version of the first SNES game had the full roster.
 * Streets of Rage 3 offers a choice between four player characters. The cutscenes shows all four heroes working together, while the game itself only supports two players at most.
 * Averted in Spider-Man and Venom: Maximum Carnage. The player is offered a few times to play as Spider-Man or Venom, which determines the next stage, but the player must control both, Spider-Man and Venom, for the final stage.
 * Also averted in The Bouncer. The three initial characters stick together and before each mission the player given the choice to select which one to control. This even leads to unique solo stages and even the chance to fight and unlock several secret characters.
 * In The Simpsons arcade game, the whole family is shown in cut-scenes trying to rescue Maggie, but how many of them are in the actual game depends on how many people are playing. The game was released in a standard 2-player version and a deluxe 4-player version.
 * The arcade version of Double Dragon 3 features a third Lee brother named Sonny who never shows up in the opening and ending sequences and seems to exist only to provide the third player a character to control. Similarly, the other playable characters are grouped as teams of siblings (the Urquidez, Chin and Oyama brothers), but the ending only shows Billy and Jimmy plus one lead member from each of the other groups.
 * The NES version of Double Dragon III changes the opening intro depending on whether one or two players are playing. Hilariously, the opening intro of the 2-Player mode misspells Billy's name as "Bimmy" in the opening, despite the fact that the 1-Player mode uses the correct spelling. However, the ending plays this straight by showing all four characters (although in the Famicom version, only the characters who survived are shown).

Fighting Game

 * Averted in the first SNK vs. Capcom: Card Fighters Clash. The opposite gender protagonist becomes a rival.
 * Super Smash Bros Brawl has this for the adventure mode. It is assumed that your current party is fighting all the enemies in the story but depending on the character limits placed as you progress, you will never see the other characters jumping in to help.

First-Person Shooter

 * At the beginning of Borderlands, the four possible player characters (Mordecai the Hunter, Roland the Soldier, Lilith the Siren, and Brick the Berserker) are all riding into town together on a bus. Once you choose which of the four you are playing, you never see the other three again. It is implied, however, that they're all teammates.
 * This can be the case.... Your team can also consist of a swarm of Brick clones, or Mordecai and Three Liliths.
 * One of the original rejected concepts for Doom involved four playable characters, complete with unique stats. In single-player mode depending on which character you selected, the other three would be killed in the opening sequence, leaving their bodies in the first room.
 * Hexen would later do what Doom hoped to do. You pick as a class Warrior/Cleric/Mage and never see the other classes again, barring multiplayer.
 * Rise of the Triad offers another interesting variation on Doom's rejected player choice concept (unsurprisingly, as Tom Hall worked on ROTT). At the beginning, the player could choose one of the five members of the H.U.N.T. to control for the entire game. This would determine the player model, voice, and relevant stats like speed of movement and how much damage the player could take. Oddly enough, the cutscenes depicted the team as operating together through the game, but only the chosen character was visible in game, suggesting that they split up and regrouped during the levels' loading screens.
 * Similar to the Streets of Rage 3 example, Turok 3 makes you choose between two characters at the beginning, and show them working together in the cutscenes even though you're always alone in the actual game.
 * Averted and played straight in Far Cry 2: some (but not all) of the other available player characters show up in the game as mercenaries that you can befriend.
 * Similar to Borderlands, Dead Island seems to assume that canonically all four characters are working together even if only one is chosen. All the characters are shown together in cutscenes.

Hack and Slash

 * Not counting Multiplayer, this happens in Diablo 1 and 2. In Diablo's Multiplayer, the NPCs keep the same speech, talking to you like if you were the sole one present.
 * This is an interesting example because, in the games' canon, all of the heroes were indeed present. The Rogue, Sorcerer and Warrior from the first game show up as Blood Raven, the Summoner, and the Wanderer (possessed by Diablo himself) in the second. Story fragments for the third game indicate that all of the heroes from the second game were involved in defeating the three Prime Evils and their armies, and they all went Axe Crazy from the ordeal (except for the Barbarian).
 * Averted in the Kingdom Under Fire games. The character you choose inevitably interacts with one or all of the alternative characters in the battles (and storylines) that ensue.
 * The title screen of Gauntlet (1985 video game) shows four heroes - the Warrior, Valkyrie, Elf and Wizard - charging monsters. You select one. This is the only hero that enters the dungeon. The only way to have all the heroes in play is if four players join up. Legends, Dark Legacy and Seven Sorrows have even more heroes and fewer possible players.
 * The Konami arcade game Devil World changes the ending depending on whether the player completes as Condor, Labryna or both. The game's U.S. release, Dark Adventure, adds a third player character named Zorlock, but only has one ending which shows all three characters (regardless of the number of people playing).

Mecha Game

 * When selectable heroes are involved in the plot, Super Robot Wars tends to subvert, invert, avert, and do the tango with this trope depending on the game in question.
 * Advance averted this; Axel Almer and Lamia Loveless both exist at the same time, and they both belong to the villains. Whoever you select ends up joining the heroes (Axel loses his memories, and Lamia is The Mole who ends up Becoming the Mask), while the other remains a villain and becomes your rival.
 * The Alpha series played with this one a lot. The Alpha 1 heroes seem to play this straight, but every duo aside from Kusuha and Brooklyn apparently got retconned out of existence when Alpha 2 came around and made Kusuha's route the canonical one. The Alpha 2 heroes also mostly play this straight in regards to each other; Arado/Seolla, Ibis/Sleigh, and Kusuha/Brooklyn don't show up in routes that aren't theirs. Sanger, on the other hand, averts this; Alpha Gaiden established his existence in all of the routes by virtue of taking place in a Bad Future. In his own Alpha 2 route, he gets woken up by an explosion and becomes the main character, but in the other Alpha 2 routes, said explosion doesn't occur and he keeps right on sleeping until the Earth Cradle unseals itself in Alpha 3, where he appears in one form or another in every route.
 * Much like Advance, Z has Rand Travis and Setsuko Ohara existing simultaneously and even trading shots with each other a few times.
 * Robot Alchemic Drive plays it straight. You're given the choice of three playable characters, and the game manual refers to them as if they're siblings. But whichever you choose, the other two will never show up, or even be mentioned.

Platform Game

 * In Mega Man ZX, your plot only includes either Vent or Aile.
 * Advent continues this; if you play as Grey, you meet Aile and she saved the world in the previous game, and if you play as Ashe, you meet Vent and he saved the world, but you never meet the other two characters. However, in Ashe's game it's hinted at one point that Grey still went through his intro stage, and a picture of both Vent and Aile is seen at one point in both stories, but otherwise the other characters never appear.
 * The Mega Man X series had this for a while. From the numbered mainstream games:
 * X4 is the closest the series gets to playing the trope straight. You can play as X or Zero, but each have their respective sides to the same story, meaning you have to play the whole game with the character you choose. Aside from one battle, both characters fight the same Mavericks. Zero calling X's escape pod in X's ending is the only time they interact.
 * X5 and X6 have this to a lesser extent (individual missions as opposed to the entire game).
 * X7 and X8 avert it by letting you switch characters on the fly.
 * As for the classic series...
 * In Mega Man Powered Up, if you choose anyone other than Mega Man or Mega, he will not show up at all outside of the ending (the Mega Man you face when playing as the Robot Masters is an Evil Twin). And Proto Man, of course, doesn't show up at all if playing as anyone other than him.
 * Mega Man & Bass plays this trope straight. This puts an interesting spin on King's fate. In Mega Man's ending, he returns home to find a letter telling him that King survived and is now fighting for justice. In Bass's ending, although we learn exactly why Wily built King, no mention of what happened to him was made, and the player assumes King perished after all.
 * In 10, if you play as Mega Man, the only time you see Proto Man is during the cutscene you get after defeating four Robot Masters. When controlling Proto Man, Mega Man appears during said cutscene, then after defeating all eight Robot Masters, Wily announces to the world that Mega Man is sick with Roboenza. But after clearing the first Wily stage, we see a perfectly healthy Mega Man running alongside Proto Man, and even stops to help the latter out when he himself falls sick. Mega Man stops appearing after that. If playing as Bass, neither Mega Man or Proto Man appear, and the only mention of Mega Man is during Wily's announcement to the world (again saying he fell sick).
 * Terramex does this.
 * In Castlevania Bloodlines, you have a choice to play as John Morris, the archetypal Belmont, or Eric Lecarde, his polearm-wielding best friend. Once you choose your character, you never hear from the other again, not even in the ending.
 * Same goes for Castlevania (Nintendo 64) and its Updated Rerelease Legacy of Darkness, which posit three people—Reinhardt Schneider, Carrie Fernandez, and Henry Oldrey—that traveled to Dracula's castle in the same year.
 * A version of this occurs in the alternate modes of the post-Symphony of the Night games: After you beat the main game, you can choose to play it again as one of the side characters (usually by entering that side character's name for your save file). However, except in two instances, the normal main character and any of the other side characters will be nowhere to be seen (and, indeed, the story elements of the main game will be stripped out completely).
 * Some of the 2D Super Mario Bros games are like this. The manual will usually say that Mario and Luigi are working together to save the princess, but this is never the case if you are playing in single player mode. Likewise with Super Mario Bros. 2 (Dolled-Up Installment of Doki Doki Panic) where the story implies Mario, Luigi, Toad, and the Princess are working together to save the world of Subcon, but yet, you can only play one character at a time per level.
 * Averted in the Sega Genesis version of Ghostbusters, you'd choose one of three Ghostbusters (Winston wasn't present for some reason). Each had their own strengths and weaknesses (Egon could run fast but couldn't take many hits, Ray was slow but could take massive damage, and Peter was a balance between both). When you chose one of them, all three would appear at the firehouse, but only one would show up in the cut scenes at the end of each level. This would imply that the other two just hung out at the firehouse while the player chosen one did all the work. In the final level, however, you'd fight the other two as boss characters because they'd been possessed by ghosts.
 * In Kirby's Return to Dream Land, Kirby is always depicted with Waddle Dee, Meta Knight, and King Dedede at his side in the story scenes, even when he's traveling alone, accompanied by Yellow, Green, and Blue Kirbies, or teamed with a mixture of the palette-swapped Kirbies and the former three characters during actual gameplay.

Roguelike

 * Averted in Nethack. You in fact see many characters in the Astral Plane. However, they all have cheap plastic copies of the Amulet of Yendor, whereas you have the real thing (hopefully).

Role Playing Game

 * Averted in Dragon Age Origins. It establishes that all other player origins actually happened (presumably including the potential player characters) but without Duncan in the right place at the right time, it's almost certain that most, if not all, ended up dead. Entirely certain, for some origins. Players familiar with alternate origins who are willing to poke around a bit can generally find a nod to the other origins somewhere—usually where a character of that origin would get extra dialogue. Such moments include:
 * If you rescue the Dwarven Commoner's friend from prison and you're not a Dwarven Noble, his friend is a rotted skeleton in the next cell over. Sorry, alterna-me.
 * Additionally, the upcoming circumstances for the Dwarven Noble origin form the basis of the Dwarven Commoner Origin plot, and the Dwarven Nobles (who's plot take place one week later) can learn the majority Dwarven Commoner origin story by talking to the Proving Trainers.
 * It can be assumed that the Mage PC either failed their Harrowing and was slain by templars, or died when the Circle Tower.
 * Jowan
 * City Elf:
 * Dwarf Noble PC: The succession crisis that occurs in the wake of the death of Endrin happens whether or not Duncan is present to rescue the exile. Bhelen kills or has Trian killed, and the second offspring of Endrin is convicted by the Assembly and exiled. The Dwarf Noble was probably killed in the Deep Roads by darkspawn, as making it to the outposts of the Legion of the Dead would have required incredible skill or luck. Endrin's "middle child" is mentioned in passing at least once.
 * The Dalish Elf PC
 * The Human Noble PC
 * The only origin story that arguably plays the trope straight (but this is due to interpretation. There is no mention of the Human Noble specifically if you use any other origin. His involvement was not necessary in any form for the attack on Highever to occur as it did. Coincidentally, it is the only origin story where the protagonist would have survived without Duncan's involvement, since Duncan doesn't show up until.
 * However, an overheard conversation in Denerim mentions the whole Cousland family being slain, which would include the Human Noble version of the Warden. (unless he went hiding somewhere else, without Duncan recruiting him. Either way, he becomes irrelevant to the story.)
 * The Dog that you recruit as any other origin is the wounded one you help, not the same one as the Human Noble one if the time line is consistent between each origin story. The dog was wounded several days before you arrive, so for it to be the same, the Human Noble's dog, without prompting, would have had to go directly to Ostagar at a faster rate than Duncan would have maintained from Highever.
 * Probably the reason the Human Noble plays it straight is because the game seems to be created with the Human Noble in mind. Regardless of race, several lines heavily imply the Warden is human (it seems out of place for a Dwarf Warden to refer to "other humans" or an Elf Warden to be told that the needs of elves need to be considered, not just humans). This origin also has the most involvement in the main plot line and is the "default" option for the Warden in DAO and DA2.
 * Happens in Mass Effect. Was there a sole survivor of Akuze if Shepard is a hero of the Skyllian Blitz? The answer is 'no'. The other characters simply did not exist. The game does however indicate that various backstory events happened regardless of where you were. For instance, while going through the Spacer background quest, your mother will refer to the attack on Mindoir ("You were in high school") which was the basis for the Colonist background. There's a subquest where you run into an survivor of Akuze who was held prisoner by Cerberus scientists - if you play a 'Survivor' yourself, he'll say some clever lines about how "The holovids say you're the sole survivor of Akuze. Who am I to argue?" before committing suicide. If you're using one of the other origins, someone will comment that there supposedly WERE no survivors of the disaster on Akuze.
 * In fact, the Skyllian Blitz is a heroic battle in which War Hero Shepard fought. In response, there was the Battle of Torfan, where Ruthless Shepard made his/her name by continuing the fight until 3/4s of his/her unit was killed, and butchered the surrendering slavers. The background events all happened from the attack on Mindoir to the Thresher Maw on Akuze.
 * Averted in most post-gen 2 Pokémon games, when you can chose a Player Character of either sex. The sprite of the opposite-gender player character becomes a Non-Player Character. Played straight in Crystal, Fire-Red, and Leaf-Green, though.
 * Also averted with the starters. Depending on the game, one or both of the starters you don't choose will end up with an NPC.
 * Horrifically/hilariously explained in this fan video. But more likely, Professor Oak keeps the third starter with him, as a Dummied Out battle with him shows. There are actually three versions of this battle programmed into the game, one with each of the starters (fully evolved) as the fifth Pokémon on the team; presumably, you would fight the version with the starter neither you nor your rival chose.
 * Played straight in the spin-off Pokémon Ranger: Shadows Of Almia where if you choose the male character the female doesn't appear (and vice-versa).
 * Arcanum: Of Steamworks and Magick Obscura allows you to create your own character or pick from a group of pre-generated ones. When the game starts, the Zeppelin crash site is littered with the bodies of whichever pre-generated PCs you're not playing as.
 * The first two Fallout offered pre-generated character with mini biographies. Whoever you did not choose never appeared.
 * Deconstructed in the Cafe of Broken Dreams special encounter in Fallout 2, where you can meet all the other player characters who were pre-generated for Fallout 1, but not "chosen" by the player or even included into the final game.
 * Same thing for Torchlight. Unchosen PCs are never seen.
 * Played straight in Lands of Lore: The Throne of Chaos. The player has a choice of four champions, each of whom has a little blurb about why he's the best choice and how the others will fail. It seems as though they are in competition. However, once the choice is made, the other three are never mentioned again. One wonders why, if the kingdom was in such great peril, they didn't just team up.
 * In the sequel, it is stated that the character Kieran has been "credited" with defeating Scotia, lending itself to the interpretation that the other three champions were also questing.
 * Averted in the Threads of Fate game which allows you to play as either Rue or Mint. Whoever does not get chosen still shows up in the game and goes on similar missions.
 * But also played straight to the effect that
 * Partially averted in Saga Frontier - You can run into (and recruit) the other playable characters, but their stats don't carry over when you play as them.
 * Played straight in both Baldur's Gate: Dark Alliance games.
 * Variation: in the original Persona, there are five possible party members - Brown, Ayase, Yukino, Elly, and (if you jump through the right hoops) Reiji. You get to recruit one of them. (Possibly two if you take the Snow Queen path, if you replace Ayase with Nanjo, the latter of which is prerequisite for the SEBEC story.) The rest? Well, who knows what happens to them?
 * The Spirit Engine 2 allows you to choose a party of three characters from a total of nine, and only the three you pick ever show up in the main story.
 * The exact same thing is true for the first game, though in that game the chosen characters are physically chosen/abducted by a fairy. The others presumably continue their boring lives.
 * Averted in the The 7th Saga. There are 7 characters that you can choose from and the other becomes NPC that can become your ally, your rival/enemy, or even a level boss!
 * Averted in Star Ocean: The Second Story. You start the game given the choice between two player characters, Claude and Rena, and whichever character you don't choose ends up in your party from the outset of the game, still has a chunk of the plot dedicated to them, and can even become the main love interest of the character you did choose if you steer their relationship in that way.
 * And, played totally straight later on when recruiting certain extra characters. If you recruit Ashton, Opera and Ernest never appear or play any role in the story, and if you wait to recruit Opera, Ashton is never seen or heard from.
 * They aren't entirely absent, at least. Ernest still appears briefly regardless, as his PA can appear long before Ashton is even mentioned. Ashton is still mentioned if you go to Salva at the appropriate time (they'll mention the fighter who went down to challenge the dragon) but he'll be Lost Forever if you don't actually go and watch him fight. It's implied that he succeeded, since no one was there to distract him, and once you come back to Salva the dragon is gone.
 * Averted in Age of Pirates 2: The City of Abandoned Ships. The other two playable characters appear in the game among the other independent captains roaming the seas; they may even be hired into the player's crew.
 * Averted hard in Seiken Densetsu 3: Not only do the characters you don't choose have their own storylines going in the background; one of them can even break you out of jail near the beginning of the game depending on the composition of your party.
 * Also averted to the maximal effect in Sword of Mana, where the characters take the same paths and face the same challenges regardless of which you choose.
 * Averted in Faery: Legends of Avalon where you get the choice of a male or a female, and you get the other one as your first companion when you set off on your quest, (you get Azielle for a companion if you play as a male and Aziel if you play as a female) either way they have a massive crush on you.
 * You can pick one or two of the six Pure of Heart characters in Darkstone to be your avatar(s). The other four apparently go off to have a beer together and laugh at you.
 * Averted in Dungeon Siege III, where the characters that you didn't pick show up later in the story with some reason of why they couldn't show up at the gathering in the beginning and can be companion characters later on.
 * In Dragon Quest IV, you choose either the male hero ("Solo") or the female hero ("Sofia"). Oddly enough, when later games reference IV (such as the Bonus Dungeon in the DS version of Dragon Quest VI), both of them show up.
 * Dragon Quest VI has another odd case regarding Schrodinger-esque characters in its Bonus Dungeon, this time referring to Dragon Quest V (again, the DS versions of both). In V, you choose between multiple women to marry and later have kids with, with the kids being the same no matter which wife you chose (except for hair color). The VI reference includes not only all three potential wives, but three nearly-identical sets of kids!
 * Averted in spectacular and still-unique-16-years-later fashion in Chou-Mahou Tairiku Wozz. Once the initial party is gathered together at the start of the game, you choose one of its members to be your player character. The rest are still part of the party, but are now secondary characters in the storyline.
 * Averted in spectacular and still-unique-16-years-later fashion in Chou-Mahou Tairiku Wozz. Once the initial party is gathered together at the start of the game, you choose one of its members to be your player character. The rest are still part of the party, but are now secondary characters in the storyline.

Shoot'Em Up

 * This trope is normally in effect for games in the Touhou Project series: the characters the player didn't select presumably still exist somewhere, they're just nowhere to be found in the story.
 * Subverted in both Lotus Land Story though, when the character you didn't select shows up as one of the bosses. Imperishable Night does something similar, but it has four storylines and only one fight with another character, so there's still several character unaccounted for.
 * Aversions: Everyone has a canonical story in Phantasmagoria of Flower View, Scarlet Weather Rhapsody, and possibly Hisoutensoku.
 * Averted in many two-player arcade gun games such as The House of the Dead series (from III onwards), the Virtua Cop series, and the Time Crisis series (from 2 onwards). The cutscenes and during-gameplay dialogue play out with both player characters exist. Though this does pose the new problem of the unused character, who does nothing while his or her partner does all the work. (Except in Time Crisis...sort of. The other player character is shown attacking alongside you, but misses every freaking shot. Watching the COM's side at the arcades shows that the enemies that the other player cannot possibly hit retreat after the other player clears his side.)
 * While the rest of the Alien Breed series play this straight (especially The Horror Continues, which is the only entry in it's series to actually feature four selectable characters), Tower Assault has a way around it: the game begins in a crash landing, and if the single player mode is chosen, whoever would be controlled by Player 2 wouldn't survive the crash.
 * Averted in the TurboGrafx-16 version of the Data East shooter Bloody Wolf. The character not chosen by the player at the start of the game will become a playable character when the initial protagonist is taken captive by the enemy.

Simulation Game

 * Averted in Harvest Moon Island of Happiness. You choose to play as either male (Mark) or female (Chelsea), and the other one appears later in the game as one of your love interests.
 * Also averted in an earlier game, Harvest Moon GB 3, where the plot revolves around you and the opposite character. The female (Sara) always owns the farm, and the male (Pete) always is a helper.
 * The creatures you don't pick in Black and White and its sequel.

Sports Game

 * There was "You" in Tony Hawk's American Wasteland. And of course, every model had the same voice.

Stealth Based Game

 * Averted with Tenchu, where the other ninja is presumably running other missions, and you have to rescue them at one point. Wholly averted with its prequel Tenchu 2, where the missions mesh together perfectly and you have to play through the game twice to get the whole story.
 * In Tenchu 3, Rikamaru will show up during Ayame's story. She does not make an appearance in his.

Survival Horror

 * Averted in Pathologic. Whoever you didn't pick would go off on their own story.
 * The original Resident Evil contains a strange example. Both scenarios start the same way: Chris, Jill, Barry and Wesker are attacked in the woods, and run towards the mansion. In Chris' mission, Barry goes missing in the game (explicitly mentioned in the intro) and Chris later encounters Rebecca of Bravo Team, who escapes with him and Jill; Barry never resurfaces. In Jill's mission, Chris is the missing person, but he's found later in a cell; Rebecca is never even alluded to, not even as an encountered corpse or in a note or file. Yet, the storyline for the sequels holds that all four of them survived the mansion incident.
 * Resident Evil 2 handles this much more clearly, which allows the player to start one character's storyline and play through the same events from the other character's perspective.
 * Resident Evil Outbreak offers eight playable characters throughout a total of ten scenarios (between the first game and File #2), with no hints whatsoever of who definitively did what and where due to the games' need to be considered a Gaiden Game.

Third-Person Shooter

 * In both Mercenaries games, you can pick one mercenary out of three to play as. The other two are never seen or heard from again. Apparently ExOps thinks that they only need to send in a single One-Man Army to do the job.
 * Well in the sequel, the other two show up shortly before the player goes on a Roaring Rampage of Revenge for the Big Bad's You Have Outlived Your Usefulness moment, but all they do is mock the player in a cantina. Apparently, their colleague getting stabbed in the back (metaphorically) and shot in the ass (literally) isn't enough to spur them to action.
 * Although, if you think about it, all characters seem to amount facing an army to "my boring Friday night": Mattias is "badass" and doesn't really care much unless he gets to have fun or has a personal vendetta so had little interest in fighting an army that has done nothing to him, Jen thinks more skilfully and about filling up her pockets so if there was already somebody taking the money she had no reason to join and have to slit when she has no steak, and the final member is laid back so he wouldn't kill an army unless he has to but is also proud so he has little need to do anything that might otherwise be work. But otherwise you could count multilayer as the "here is your help" from them.
 * Alien Swarm has this trope even if there are 4 players in the game. There are 8 characters to play as but only 4 at a time can be played, leaving you to wonder what happened to the other 4 characters.

Turn-Based Strategy

 * Averted in the turn based strategy game Dark Wizard for the Sega CD. The player picks which hero to play, but the ones he didn't choose will appear during the course of the story as one-off NPCs with a single line of dialogue.
 * In the second part of the fourth Fire Emblem game, Genealogy of the Holy War, you take control of either the children of characters from the first part, or, if a character never got married, a set of replacements that bear no relation to anyone from part one. While it's obvious why offspring don't appear if their potential parents never got hitched, it's unclear where the replacements are (or if they even existed at all) if they did actually marry.

Literature

 * Choose Your Own Adventure books have this, too. One of the Fighting Fantasy books "The Legend of Zagor" does it. You pick one of four characters. Whichever you pick is the only one present in this adventure.
 * Also used in the reissues that let you pick a pre-generated character.
 * Also used in the Fabled Lands books, though it's possible the others are adventuring.