An unlockable character (also referred to as a secret character or hidden character, and in-game as challengers, or newcomers in the N64 game's Backup Clear menu) is one that is not available at the start of the game (unlike a starter character), but instead must be received in-game (unlike downloadable characters) through other means.
Unique criteria must be met in order to unlock each character, as outlined below. Once such criteria are met, the challenger will appear the next time the player returns to the menu. If the player wins the subsequent battle, a message will appear congratulating them for unlocking the new fighter.
In Super Smash Bros., the character select screen displayed placeholders for not yet unlocked characters. This was changed in Melee, where the clones didn't have placeholders prior to unlocking, with their portraits simply appearing afterward. The placeholder slots were completely removed from Brawl onward.
In Super Smash Bros. 4 and Super Smash Bros. Ultimate, whenever a character is unlocked, a "[Character] Joins the battle!" screen is displayed while playing Rare Trophy from Melee, before archiving their corresponding milestones. This also applies to downloadable content characters once they are downloaded, or when the game is booted after a character's release date in case of being purchased them via Fighters Pass in the latter game.
"Challenger Approaching!" screen
The "Challenger Approaching!" (挑戦者が現れました！, A Challenger has Appeared!) screen is a message that will be displayed after the player has met a criteria required to unlock any of the available characters. Every game has its unique screen.
The original game had a silhouette of the character merely displayed in a blue box in front of a black background, with an exclamation point in a red circle on the top of the screen, and the phrase "Challenger Approaching" next to it. The screen uses similar music to the 1P-Game's intro, with the only difference being the absence of drums for the "challenger approaching" tune. As a result, this is the only game where the challengers' silhouettes are animated, showing them in their fighting stances while rotating (like in the character select screen), rather than just shadowed versions of their official illustrations.
Melee added the phrase "A new foe has appeared!," and also had a silhouette of the approaching challenger. The poses for the challengers were silhouettes of their renders when selected on the Character Select screen (some, however, like Luigi and Ganondorf's, were their renders from inside the boxes). The game also added animations to the screens, with an undulating matrix effect in the background, while the exclamation point, text and silhouette would be eased in. Original music was also provided solely for the screen, which took the sound of a slow, ominous siren.
Brawl returned to the plain black background (there would be a silhouette of an unlockable character the player would face); but this would only occur if the SSE method was not used. Also, Brawl removed the word "Warning" and the circle explanation point logo from the challenger approaching screen. It still had animations that would ease in, and when the player pressed any button, the images would fade to black, while the "Challenger Approaching!" text would scatter all over the screen; the siren is also considerably faster and more panicky in its sound than how it sounds in Melee.
Smash 4 reused Brawl's warning siren, but there are some differences in both versions. The 3DS version added in considerably more colors, including hues of green, black, and violet; the screen also says "A challenger approaches!" instead of its previous quotations. The Wii U version uses a font style similar to the ones in the newcomer trailers, and the background contains a picture of a supernova; the text is nonetheless reused from past games. The unlockable character in both versions of Super Smash Bros. 4 on the screen is still a silhouette that the player would face (just like in the previous three installments).
As in Smash 4, the warning siren from Brawl is used in Ultimate. This time there is a dark pink background with a white/pink light shining behind the silhouette of the unlockable character. The text about unlocking characters remains the same from prior games.
After the "Challenger Approaching!" screen, the unlockable character will then be fought in an ordinary one stock match with no time limit, on a predetermined stage with predetermined music. The AI difficulty of the duel depends on the game, usually at low difficulty for the first fighter, then it gradually increases with every fighter unlocked, however, it is reversed in Melee, and always high in the Wii U version of Smash 4. The player uses the last character played as, including the last used costume. In the case of multiplayer battles, in the first three Smash games, the player who won the match will fight the challenger; if a CPU wins the match, the challenger will not appear. Super Smash Bros. 4 changed this formula such that if a CPU wins the match, then the human-controlled player with the highest rank will battle the challenger.
By defeating the opponent, the character becomes playable. If the player fails, however, they will not unlock the character, but in the next battle they win, they are guaranteed to meet with the challenger again.
The "Challenger Approaching!" screen has become somewhat of a meme in the Smash community. Many digitally manipulated versions of these screens have appeared, often featuring characters who do not appear in the games, mostly using artwork of the character from another game instead of original artwork (which gives away its falseness). The screens became so popular that they were featured as part of the DOJO!!; in earlier updates, whenever a new character was introduced, a banner that said "Warning! Challenger Approaching!" would appear above the entry.
Challenger Approaching Screens
Challenger Approaching Alarms
Masahiro Sakurai has stated that it would be appropriate for third-party characters to be unlockable characters. In Super Smash Bros. Brawl, the first game to feature third-party characters, both third-party characters (Solid Snake and Sonic the Hedgehog) are unlockable characters.
In addition to the challenges and versus match method of unlocking, all unlockable characters can be unlocked by playing through The Subspace Emissary. The majority of these characters are unlocked as part of the linear story of SSE. However, Toon Link, Wolf, and Jigglypuff are only unlockable after the main SSE gameplay is completed by finding a secret area while replaying levels. Once a character joins a group of playable characters, the character will be instantly unlocked for normal play (without requiring a "Challenger Approaching" battle). However, some characters, as per the SSE's story, must be battled before they will join the player's party, such as Lucario (depending on the path chosen in The Glacial Peak).
The Subspace Emissary consists of 31 different stages. As some stages share the same name, the earlier stage is denoted with a I while the later-appearing stage is followed by a II.
Sonic is the only character who can be unlocked four different ways.
When only one character is available in Co-op mode, the character has two different colors. This happens in nine stages, with eight or nine characters: Mario (in the Midair Stadium if he was chosen in the battle with Kirby, curiously only happens in this battle), Kirby (in the Midair Stadium, in the battle with Petey Piranha, and occasionally in the battle against Mario, and in the Subspace II, all stage), Pit (in The Skyworld, before having Mario join), Lucas (in The Ruined Zoo, before joining Ness and Pokémon Trainer), Marth (in The Battlefield Fortress, before joining Meta Knight and Ike) Zero Suit Samus (in The Research Facility, I before she joined Pikachu), Meta Knight/Lucario (in The Glacial Peak, only in the battle against Lucario/Meta Knight), Snake (in the Battleship Halberd Interior, before he joined Meta Knight and Lucario) and King Dedede (in the Subspace I, only in the battle against Bowser). This does not happen when there is only one player, but this might happen when there are two players.
The inclusion of Wendy O. Koopa (as one of Bowser Jr.'s alternate costumes) and Lucina as unlockable characters makes them the first female characters to be unlockable. After every tenth VS. match, the player gets to challenge an unlockable character, starting with Ness and finishing with Jigglypuff when 120 matches are played.
In addition to the characters below, Mii Fighters are not shown on the character select screen until the player has created at least one. However, since the ability to create Mii Fighters is granted from the beginning, the characters cannot truly be called unlockable.
Despite Duck Hunt having a home stage of the same name added into the game in the 1.1.1 update, they will always be fought on Battlefield for their unlocking battle regardless of which version of the game is being played.
Unlike Super Smash Bros. for Nintendo 3DS, Ness, Jigglypuff, Ganondorf and Bowser Jr. are starter characters. Like the 3DS version, a character is unlocked for every ten versus matches played starting with Falco. Two exceptions to this are Mr. Game & Watch and Duck Hunt, which they need 20 more versus matches than R.O.B. and Mr. Game & Watch, respectively. Unlike the previous three installments (Melee, Brawl, and the 3DS version), no Super Smash Bros. universe stages are used for challenger approaching battles. Instead, all unlockable characters use a stage from their respective universe except for R.O.B., in which he uses the Wrecking Crew stage due to him not having a stage from his own universe.
In addition to the characters below, Mii Fighters are not shown on the character select screen until the player has created at least one. However, since the ability to create Mii Fighters is granted from the beginning and there is no Challenger Approaching fight, the character cannot truly be called unlockable.
The starting roster in Super Smash Bros. Ultimate comprises the eight starter characters from the original Super Smash Bros. game, with all other fighters being unlockable or downloadable. There are two ways to unlock characters: by defeating them in a Challenger Approaching fight, or by awakening them in the World of Light. With the vast majority of the roster being unlockable, unlocking characters is advertised as a core feature of the game; no characters are left "secret" like in previous games, and character unlocks are designed to occur at a more streamlined and consistent pace than in previous games.
In the World of Light, only characters that have been awakened in that mode can be used, with only Kirby initially being available. However, awakening a fighter in the World of Light that is not a starter character also unlocks them for the regular roster as well.
In a Challenger Approaching fight, the character must be fought in a one-on-one fight, with the stage and music being specific to that fighter. The difficulty of Challenger Approaching fights start out at being very low, but progressively increases with each character unlocked. If the player loses the fight, they can redo the Challenger Approaching fight via Challenger's Approach on the Games and More menu after a few minutes pass.
All characters except Mii Fighters can be unlocked in a Challenger Approaching fight. Instead, each Mii Fighter can be unlocked by creating a custom Mii Fighter of that type. However, Mii Fighters may also be unlocked by awakening them in the World of Light.
When the player finishes a VS. match, a Mob Smash, a Spirit Board fight or exits the World of Light, a new character can challenge the player to a Challenger Approaching duel. However, the player must then wait 10 minutes before a new Challenger Approaching challenge will be issued. This 10 minute cooldown can be bypassed by closing the game and reopening it.
Time-based Challenger Approaching challenges are issued in a specific order, skipping any characters unlocked in the World of Light or whose Challenger Approaching fight has already been triggered due to Classic Mode.
When the player completes Classic Mode with a given character, a new character will challenge the player to a Challenger Approaching duel. All of the eight starter characters have their own character unlock trees, each with eight characters to unlock, except for Pikachu, who has seven. The challenger is determined by the 1st Player character's assigned tree, and will be the next character from the top of their tree down (as indicated on the table below) who has not already been unlocked or issued a Challenger Approaching duel.
When all the characters in a tree are unlocked, completing Classic Mode with those characters will unlock the next available character in Mario's tree, then Donkey Kong's, and so on. Completing Classic Mode with downloadable fighters will also unlock fighters in this order, as these characters are not assigned an unlock tree.
The Challenger Approaching duels are the same as those issued on a timed basis, this is simply another way to trigger them. Notably, all clones, semi-clones, and pseudo-clones except for Ganondorf, Roy, and Chrom are in the same tree as the character they are based on.
Below is a table listing the stage and music for each character's unlock battle. It also includes the order they are unlocked in as time-based challenges.
The values listed under "Cumulative Wait Time" are idealized values that assume that no characters are unlocked in the World of Light or have their Challenger Approaching fights triggered by Classic Mode, that the player never closes the game after first opening it until they trigger Palutena's Challenger Approaching fight, and the player never spends longer than the minimum amount of time (10 minutes) between triggering Challenger Approaching fights.
World of Light
In World of Light, each fighter must be unlocked through a fighter battle, with a few exceptions:
The fighter battles all feature the same single condition: Win the battle to awaken the fighter