History Main / ViralUnlockable

* ''VideoGame/Warzone'' has the "Viral Achievement", which is earned by defeating someone who already has it.

* Beating a developer from Creator/NetherrealmStudios in an online match in VideoGame/MortalKombat11 grants you an exclusive "Dev Slayer" icon and calling card set for your profile.

* ''VideoGame/{{Splatoon}}'' and ''VideoGame/Splatoon2'', it's possible to order pieces of clothing gear from the other players in your plaza. Upon placing an order, you'll be able to purchase a copy of that gear item from Spyke or Murch the following day. While this system does have its limitations -- some items that are obtained as part of promotional events or unlocked in the single-player campaign cannot be ordered -- several gear items that would otherwise be unobtainable TemporaryOnlineContent can still be acquired through this method.

* The concept of an [[https://en.wikipedia.org/wiki/Erdos_number Erdős number.]] Mathematician Paul Erdős had a number of 0. Anybody who has worked directly with him is given the number 1. Working with somebody who has an Erdős number of 1 grants one the Erdős number 2, and so on. In a similar vein, the concept of [[https://en.wikipedia.org/wiki/Six_Degrees_of_Kevin_Bacon#Bacon_numbers Bacon Numbers]] calculates the distance between an actor and Creator/KevinBacon.

* The ''VideoGame/{{crossbeats}} REV.'' song "Blue Destiny Blue Eternal" can only be unlocked by playing a multiplayer session with someone who has the song unlocked, and then playing the song in said session.

* In ''[[VideoGame/PokemonRubyAndSapphire Pokémon OmegaRuby and AlphaSapphire]]'', the Eon Ticket item (allowing the owner to battle Latias or Latios depending on version) was distributed via [=StreetPass=], meaning that getting it required you to be near someone else who had the Ticket and who had their 3DS with them. This made getting it fairly easy in populated areas, but ''very'' difficult for players who were more isolated.

* The concept of an [[https://en.wikipedia.org/wiki/Erdos_number Erdos number]]. Mathematician Paul Erdos had a number of 0. Anybody who has worked directly with him is given the number 1. Working with somebody who has an Erdos number of 1 grants one the Erdos number 2, and so on. In a similar vein, the concept of [[https://en.wikipedia.org/wiki/Six_Degrees_of_Kevin_Bacon#Bacon_numbers Bacon Numbers]] calculates the distance between an actor and Creator/KevinBacon.

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* ''VideoGame/HearthstoneHeroesOfWarcraft'', as a reference to the Corrupted Blood incident, made the Hakkar card back unlockable for most players by playing against anyone else who has the Hakkar card back. It also automatically switches your card back to that, so you could be unintentionally spreading it if you didn't check.

* In ''VideoGame/SuperSmashBros: Brawl'', playing online against a secret character unlocks that character instantly.

* Some title cards in the ''VideoGame/CallOfDuty'' series are unlocked in this manner. For example, the "STD" and "Infected" titles in ''VideoGame/CallOfDutyModernWarfare2'' and ''[[VideoGame/CallOfDutyModernWarfare3 3]]'' are earned by using your knife to kill someone who has the title equipped.
* ''Videogame/PAYDAY2'' has the mysterious "Virus" achievement. Its only description is you need to play with someone who owns that achievement to get it.

* The concept of an [[https://en.wikipedia.org/wiki/Erdos_number Erdos number]]. Mathematician Paul Erdos had a number of 0. Anybody who has worked directly with him is given the number 1. Working with somebody who has an Erdos number of 1 grants one the Erdos number 2, and so on. In a similar vein, the concept of [[https://en.wikipedia.org/wiki/Six_Degrees_of_Kevin_Bacon#Bacon_numbers Bacon Numbers]] calculates the distance between an actor and Creator/KevinBacon,

* Several ''VideoGame/{{jubeat}}'' games allow you to unlock songs simply by playing them in local or online multiplayer rather than through their "proper" unlock conditions; in the case of online, you pick a "matching select" option instead of a specific song and the game will pick a song that others on the network are currently waiting to play. In fact, one song could be unlocked by online-matching with particular ''members of Konami staff'', although the usual "pick matching select" and "have someone else pick it in local matching" methods work too.

* Several ''VideoGame/{{jubeat}}'' games allow you to unlock songs simply by playing them in local or online multiplayer; in the case of the latter, you pick a "matching select" option instead of a specific song and the game will pick a song that others on the network are currently waiting to play. In fact, one song could be unlocked by online-matching with particular ''members of Konami staff'', although the usual "pick matching select" and "have someone else pick it in local matching" methods work too.

* The ''VideoGame/{{crossbeats}} REV.'' song "Blue Destiny Blue Eternal" can only be unlocked by playing a multiplayer session with someoen who has the song unlocked, and then playing the song in said session.

** The Tinsel and Shimmer-scale breeds are only available as contest prizes or having it bred from a winner. For a long time all Tinsels and Shimmer-scales on the site were bred from the original 5 gold/10 silver/15 bronze Tinsels and 10 gold/20 silver/30 bronze Shimmer-scales, but they have since been made much more obtainable (e.g. monthly raffle).

Because of the obvious Catch22Dilemma involved with this trope, ''someone'' has to get it some other way [[PatientZero so they can spread it to normal players]]. Methods includes time-limited events, an alternate (often much more difficult) goal, or some people (usually staff members) being given it immediately.

Because of the obvious {{Catch 22 Dilemma}} involved with this trope, some people (usually staff members) usually have the item in question unlocked from the start so they can spread it to normal players.

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* The Creeper Clunk skin from ''VideoGame/{{Awesomenauts}}'' is unlocked by killing a player who is playing as Clunk and is wearing the skin.
* ''VideoGame/BrutalLegend'' has the "Six Degrees of Schafer" achievement, which can only be obtained by playing an online game against someone who already has it (with the original vector being, of course, Creator/TimSchafer).
* Some title cards in the ''VideoGame/CallOfDuty'' series are unlocked in this manner. For example, the "STD" and "Infected" titles in ''VideoGame/CallOfDutyModernWarfare2'' and ''[[VideoGame/CallOfDutyModernWarfare3 3]]'' are earned by using your knife to kill someone who has the title equipped.
* The post-game DLC quests for ''VideoGame/DragonQuestIX'' have become this since the DS' Wifi Connection servers were disabled- the quests can still be unlocked via local wireless connection with a player who already has them, making them one of the few bits of DS DLC that can still be legitimately obtained post-shutdown.
* In ''VideoGame/HeroesOfTheStorm'', Cho'gall was initially released in this way - [[MechanicallyUnusualFighter a two-headed character controlled by two players at once]], you could play as one of the heads as long as someone who had unlocked him was playing the other. After doing this, he was unlocked for your own use.

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* In ''VideoGame/SuperSmashBros: Brawl'', playing online against a secret character unlocks that character instantly.