The remaining cast is Ridley, Impa, Dixie, Chorus Kids, and Mewtwo
Ridley is the reverse of Little Mac, essentially
He fights poorly on land, good in the air
He mostly fights up close, except he has aimable projectile fireballs
Dixie is a MOSTLY Diddy clone, 'cept for that she uses her ponytail for recovery, and most of her smash attacks
Impa is a heavy Sheik Clone, her biggest standard moveset changes being her use of her giant sword for her Side B, creating a wake of damaging waves behind her
She also has a different teleportation attack, using a deku nut to "flash" from place to place instead of a smokescreen, breifly stuns those near her
Ness gains most of Lucas' airgame and some of his smash attacks.
Dark Pit uses beam claws for side Smash
Dark Pit has a cannon for final smash
And palms for one of the custom moves
Mewtwo receives MAJOR buffs and a new Side smash, being Psycho Cut
Prince Fluff (as TankBot) is an assist.
Weavel from Metroid Prime Hunters is an assist, seperating and terrorizing opponents
Goku (from Yuyuki, NOT Dragon Ball Z) Is an assist due to "fan demand"
Boom Boom is an assist; thrashing about on one platform, occasionally flying to another
Goombella is an assist, giving humorous "tattle" comments on opponents during the battle (like Ressetti but with character specific comments)
Cat Toad was a planned assist, leaker says it was on a shortlist of assists to get the ax when he last checked
A Water Wraith from Pikmin is also an assist, mowing over opponents; "wheels" can be destroyed; making the assist useless
King Hippo from Punch out is an assist. He goes rather slowly, but is extremely powerful and can likely KO and players close to him.
Another among the shortlist for the ax was Fi, likely replaced with Ghirahim
Sumia is an assist, flying around on her pegasus and stabbing opponents with her lance; occasionally throwing a Javelin
Tiki is an assist, turning into a dragon and spitting fire at opponents
Landia is an assist, allowing you to ride it (Not unlike Gogoat) and fly around, spitting projectile fireballs at opponents
The final assist I was made aware of that hasn't been revealed is Black Shadow; plows through opponents with his Dark Schneider
Basically all Pokeball Pokemon were shown off in the Greninja trailer; but I will elaborate, nevertheless
Chespin uses Seed Bomb
Oshawott uses Razor Shell
Snivy uses Vine Whip and Grass Knot
Darkrai is in, uses Nightmare akin to the anime to lull enemies to sleep and inflict damage on them whilst they're unconscious
Floralia is a new Kirby stage for 3DS; A magic beanstalk weaves it's way across the various worlds; occasionally enemies in the background act as hazzards
Magicant is another stage for 3DS; the stage's dreamlike effect causes alterations to the gameplay, mostly time and physics effects
The Gameboy stage switches between old Gameboy games, the "NINTENDO" logo acts as a platform, but it doesn't reappear immediately after the stage re-transitions
Most of the new stage information I have is for Wii U
The new Star Fox stage behaves like Corneria and Area Z, but with less camping potential
Super Bell Hill is also a new stage, coins arupt from the pools from either side and can be collected, but unlike Golden Plains, it doesn't do much
Cat Goomba's occasionally wander onto the stage and can pounce players
Lor Starcutter and City Trial are new stages; Lor Starcutter is like a cross between the Halberd and Corneria stages, eventually crossing into Another Dimension, where Magolor attacks the cruiser
City Trial behaves like Skyloft, switching between City Wharf, Green Canvas, Electric Lounge, and more.
K.K. Slider and DJ K.K. appear on the "Town and City" stage akin to K.K.'s cameo in Brawl. They both ride on the platform the fighter's are on. After so long during a battle featuring DJ K.K., He will play an electronic remix of the victory theme of the fighter who's currently in first.