Unlockable character

An unlockable character is a character 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 mystery character that he's about to face. By winning the challenge and defeating the opponent, the character becomes playable. In it will be the same although the tasks the player must complete to unlock the characters are still unknown.

Super Smash Flash 2
There are no unlockable characters as of demo v0.9b.

Trivia

 * When Black Mage was revealed to be playable in demo v0.7, he was surprisingly added as an unlockable character who could be unlocked by playing ten Brawls.
 * Similarly, Captain Falcon was unlockable in demo v0.8 by winning a single Brawl match with every other character.
 * In demo v0.9, Jigglypuff who is unlocked by completing all the events in the demo.