Greninja

How Greninja joined the Tourney
Greninja, the ninja pokemon is one of the most skilled Ninjas, obtaining the high rank of Special S-Class when he was a Froakie. Little is known about him besides the fact he is the Ninja's best assassin.

How to Unlock
The player must complete one of the following requirements to unlock Greninja: For both of these options, the player must brawl Greninja on the Pokemon Stadium IV stage. After defeating Greninja, the announcer will say "Someone else has joined the Tourney!" after a Smash Ball appears on the lower-right corner of the screen with a message saying "You can now use Greninja, the Ninja Pokemon!"
 * Play 770 matches in the Versus Mode.
 * Clear Classic Mode in less then 50 Minutes.

Water Shurikens (Neutral)
Greninja takes two shurikens and throws it at his opponent. You can tapping the B button to bring more Shurikens.

Shadow Sneak (Side)
Greninja dissapears, then reappears and attacks the opponent with his kunai.

Waterfall (Up)
A torrent of water appears that Greninja "surfs" on top of.

Double Team (Down)
Greninja enters a defensive tai chi-like stance. If it is attacked during this stance, it will teleport behind the attacker, then counterstrike with a sliding kick for moderate damage and surprisingly high knockback, which is even greater after Greninja has taken damage.

Hyper Water Shurikens (Hyper Smash)
Same as Water Shurikens, except much stronger and brings 10 Shurikens.

Hydro Cannon (Final Smash)
Greninja crouches and opens its mouth. Then, a glowing light blue ball of water appears in front of Greninja's mouth and Greninja fires it at the opponent.

Trivia

 * His english voice shares with Goku.
 * His japanese voice shares with Patroklos.
 * Greninja is the first pokemon character from the new Generation VI game, Pokemon X and Y.
 * Yin, one of Yo's Woo Foo Knights is Greninja's rival.