Expansion character

An expansion character, also known as downloadable character, or simply DLC, is the concept for a playable character in Super Smash Flash 2 that is not normally accessible in the default game. Instead, these characters are developed separately from the main game, requiring to download an extension in order to install the character into the game once finished. With this concept, characters that did not get into the official roster would be added by other developers even after the game finishes development.

Expansion characters were originally sorted into two categories: "official" and "unofficial". "Official expansion characters" would be those created directly by the developers, receiving extensive feedback (akin to new characters revealed at major tournament events) and would have been available for online play whereas "unofficial expansion characters" would be those created by fans, requiring coding assistance by a developer to properly include them into the game and would have not been available for online play.

"Official expansion characters" were revealed in old versions of the Smash Flash DOJO!!! but were all removed with the constant overhauls in the DOJO!!!. Currently, the game does not support expansion characters, as the concept was initially dropped after the game's first major revamp following the 2011 demo, v0.7. However, it has been confirmed that expansion characters will likely become available following the release of the final version. There is also evidence of "XP" characters contained within the game's files, as an expansion slot can be hacked into the game (though non-functional).

There was also originally an official forum called the Super Smash Flash 2 Expansion Forums where users could indirectly or directly develop, suggest, and discuss expansion characters. However, the forum was eventually disaffiliated from McLeodGaming and closed soon after.

List of expansion characters
Below is a list of the official expansion characters revealed via the old DOJO!!! versions. None are currently planned to be released.

Dark Sonic
Dark Sonic is a dark super transformation achieved by Sonic the Hedgehog in the anime Sonic X, appearing only in the episode "Teasing Time". The multitude of fake Chaos Emeralds and Sonic's intense anger allowed him to achieve this transformation. Dark Sonic seems to have two forms: a mid-transformation and a complete transformation, with the latter Super Sonic, except his back quills are longer, he has a dark blue aura around him, his eyes have no pupils or irises, and his fur and skin are black.

Dark Sonic was planned to appear in SSF2 with custom sprites based on its complete transformation. His moveset would have incorporated various psychic powers, similarly to Shadow the Hedgehog's planned moveset at the time.

Ike
Ike is the central character of Fire Emblem: Path of Radiance and one of the main characters in Fire Emblem: Radiant Dawn. He is the son of Greil and Elena, as well as the older brother of Mist. He is also the leader of the Greil Mercenaries and the first (and only) main character in the  series who is not of noble birth.

Ike was planned to appear in SSF2 with custom sprites resembling those from the Fire Emblem games for the Game Boy Advance. His moveset would be based on his moveset from Super Smash Bros. Brawl, in which he wields Ragnell and delivers slow, powerful attacks.

NES Mario
NES Mario is an unofficial term referring to Mario during the events of Super Mario Bros., where Mario and Luigi attempted to stop Bowser's reign of terror by defeating seven False Bowser's and then freeing several Toads imprisoned by the False Bowsers. Mario and Luigi were, afterwards, able to defeat the real Bowser, release Princess Peach, and return her to the people of the Mushroom Kingdom.

In SSF2, NES Mario was planned to appear with custom sprites based on his 8-bit appearance from Super Mario Bros., specifically as Super Mario. His moveset would feature his abilities from that game, such as kicking Koopa shells, and it was hinted to feature other classic characters that would appear with their original sprites, including Bowser, an Excitebike racer, and a Medium Invader from Space Invaders.

Roy
Roy is the main protagonist of Fire Emblem: The Binding Blade. He is the son of Eliwood, the main character of Fire Emblem: The Blazing Blade. Roy's inclusion in Super Smash Bros. Melee marked his very first appearance, which also sparked interest in the Fire Emblem series in the West and was responsible for Nintendo's decision to release the games internationally from that point onwards.

Roy was planned to appear in SSF2 with sprites ripped from his appearance in Fire Emblem: The Binding Blade. His moveset would be based on his moveset from Super Smash Bros. Melee, in which he wields the Binding Blade and delivers powerful attacks.

Sephiroth
Sephiroth (セフィロス) is the main antagonist of FINAL FANTASY VII and one of the major antagonists in its extended universe. In spin-off appearances, Sephiroth is depicted as Cloud Strife's archenemy and is seen as a symbol of Cloud's troubled past that haunts him. Sephiroth is a former renowned SOLDIER who eventually became twisted. He is briefly a party member during a flashback in FINAL FANTASY VII and is both the penultimate and final boss in the game.

Sephiroth was the first expansion character to be revealed for SSF2, and he would have used custom sprites based on his appearance in FINAL FANTASY VII. His moveset was planned to incorporate fast, long-ranged attacks with the Masamune, as well as various Materia-based attacks. He was initially intended to be released in the summer of 2008, but this never occurred.