An unlockable character is a character in the Super Smash Flash series that is not available at the start of the game (unlike a starter character), but must be unlocked. Unique criteria must be met in order to unlock a certain character. In both Super Smash Flash and Super Smash Flash 2, typically, the player must accomplish a particular in-game feat and once complete, a message will display: "Warning! Challenger Approaching!" with a white question mark block over the black silhouette of the unlockable character.
By completing the in-game feat and defeating the opponent in a 1-stock match, the character becomes playable. In the original Super Smash Flash, this matches would always take place on Final Destination, but in Super Smash Flash 2, each character is fought on a different stage; their home stage.
In Super Smash Flash
|Blue||McLeodGaming||Clear Adventure with Blade on normal difficulty or higher.|
|Cloud||FINAL FANTASY||Complete 100-Man Melee.|
|Crono||CHRONO||Clear 3-Minute Melee.|
|InuYasha||InuYasha||Clear Adventure without losing any lives.|
|Jigglypuff||Pokémon||Clear Adventure on any difficulty with any character.|
|Lloyd||Tales||Clear Adventure with any character after having one hour of total play time.|
|Luigi||Mario||Clear Adventure with Mario on normal difficulty or higher.|
|Mewtwo||Pokémon||Clear Adventure mode with Pikachu and Jigglypuff on normal difficulty or higher.|
|Mr. Game & Watch||Game & Watch||Clear Target Test with every character but him.|
|Mr. Incredible||The Incredibles||Clear Classic with all 13 starter characters.|
|Naruto||Naruto||Clear Adventure with all 13 starter characters.|
|Shadow||Sonic||Clear Adventure with Sonic, Tails and Knuckles on any difficulty.|
|Super Sonic||Sonic||Clear Classic with Sonic on any difficulty without continuing.|
|Young Link||The Legend of Zelda||Clear Classic with Link on any difficulty.|
|Zero||Mega Man||Clear Adventure with Mega Man X on Normal difficulty or higher without continuing.|
In Super Smash Flash 2
|This section contains information for a confirmed feature that is not currently available.
The subject was confirmed by an official source, but is not present in the current version of the work bound to appear. Instead, it is meant for a future update. Any information is subject to change.
It was confirmed that all characters added after the initial release of Beta 1.0 will be unlockable in the full version of SSF2.
|Pichu||Pokémon||Play a match in any game mode (except for training) in which a player-controlled Pikachu accumulates at least 172% damage.||Pokémon Colosseum|
|Sandbag||Super Smash Bros.||Complete Classic using a random character on Normal difficulty or higher without using continues, or play against a player online who has beaten a developer.||Waiting Room|
In demo versions
These three characters were unlockable in early demos for the sake of their initial inclusion in SSF2.
|Black Mage||FINAL FANTASY||Play 10 Group matches.||Chaos Shrine||0.7|
|Captain Falcon||F-Zero||Win a Group match with every other character but him.||Sand Ocean||0.8a|
|Jigglypuff||Pokémon||Clear all original 10 events.||Pokémon Stadium 3||0.9a|
- In the original "Warning! Challenger Approaching!" screen for SSF2, the silhouette of the McLeodGaming's fist logo could be seen.