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. A unique criteria must be met in order to unlock a certain character. Typically, the player must accomplish a particular in-game feat and once complete, a message will display: "Warning! Challenger Approaching!" with a silhouette of the character the player is about to face. The unlockable character will then be fought by the last character Player 1 had used. By winning the challenge and defeating your opponent, the character becomes playable.

Characters
* The time required to unlock Mewtwo in calculated in "player-hours" (eg. 2 human players gives 2 hours for every hour of game-time, 3 human players give 3, and four players give 4).

Super Smash Bros. Brawl
Masahiro Sakurai once stated that he feels that it would be appropriate that third-party, or "guest" characters, like Solid Snake or Sonic the Hedgehog, would be unlockable. This became true when Super Smash Bros. Brawl came out on March, 9, 2008.

Also, all unlockable characters can be unlocked by playing through The Subspace Emissary. 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 to before they will join your party.

Characters
** Toon Link, Jigglypuff and Wolf are not part of the main plot of Subspace Emissary, players must beat the main story first then revisit certain stages to find them that way.

*** Sonic is the only character who can be unlocked 4 different ways.