'Super Smash Bros.' to gain first downloadable character; still not Krystal
March 31 is the deadline for player's chance to download Mewtwo as a playable character in Super Smash Bros. for the 3DS and Wii-U. Mewtwo will become the first downloadable fighter in the Super Smash Bros. franchise, Nintendo's mascot fighting game. In order to obtain the character, players must join Club Nintendo and register copies of both the 3DS and Wii-U versions of the game. Despite the deadline of the end of the month, the actual character will not be available until a later, still unspecified date sometime this spring.
There are currently no plans for further downloadable characters; though it is entirely within the realm of possibility, Club Nintendo's discontinuation makes it an unlikely possibility. Blue vixen fans will just have to wait (and hope) for the next console.
Update (April 1): Mewtwo will be available April 28, and further downloadable characters have been verified (though, once again, not Krystal). [Sonious]
Update 2 (April 2): There is now a system in place for voting on characters; I forgot who I picked. It is available until October, so don't expect a quick turnaround. Also, the March 31 deadline was only for a free Mewtwo; Mewtwo will be available for $3.99 for one game or $4.99 in bulk.
Mewtwo first appeared in the original pair of Pokémon games, Red and Blue (or Red and Green in Japan), as a after-game "legendary" Pokémon. Though the Pokémon series is popular with the furry fandom, Mewtwo's back story makes him furrier than most Pokémon, as he is an experimental "uplifted animal," though in this case the animal uplifted happens to be a pink, vaguely cat-like Pokémon, rather than a real animal.
Mewtwo was unlockable in the second Smash Bros. game, Melee, but he has not returned, until now, in any other installments. His cut from the roster was surprising, as he was the only non-returning character from Melee to have a unique special moveset, rather than a "cloned" special moveset from another character. However, Mewtwo was not seen as one of the more successful characters to play competitively, ranking 21 out of 26 characters on at least one tier list.
With the addition of Mewtwo, the Pokémon franchise is tied with the Super Mario Bros. franchise as the most represented in the latest installments, with six fighting characters apiece. Other franchises represented in the game with furry characters include Duck Hunt and Star Fox, Super Mario Bros spinoff franchises Donkey Kong and Yoshi's Island, as well as the third party guest franchise Sonic the Hedgehog. For a full list of furry characters appearing in the latest game, see here (though readers who consider unlockable characters in a game without a plot spoilers should avoid).