Yes progress is slow but out of 130 characters on the base roster I already got done 50 of them so far.
The current roster plus DLC for the first season:
Mario
Luigi
Peach
Bowser
Yoshi
Toad
Donkey Kong
Diddy Kong
Daisy
Rosalina
Wario
Waluigi
Link
Zelda
Ganondorf
Midna ***NEW***
Girahim **** NEW***
Fox
Falco
Samus
Ridley
Pikachu
Jigglypuff
Mewtwo
Zubat
Brock (W Onyx and Geodude)
Marth
Villager
Kirby
Meta Knight
Dedede
Sonic
Tails
Knuckles
Amy
Shadow ****NEW***
Eggman
Bayonetta
Arle ***NEW****
NiGHTS
Mega Man
Bass ***NEW***
Ryu
Ken
Chun-LI
Morrigan
Jill
Dante
Strider
Cloud
Sora
Slime
Pac-Man
Kazuya
Heihachi
Ivy
Yuri
Klonoa
Terry
Kyo
Mai ***NEW***
Scorpion
Shantae
Simon Belmont
Bomberman
Snake
Kratos
Bart
Homer
Marge
Lisa
Krusty ****NEW****
Spongebob
Timmy Turner
Peter Griffin
Stewie
Brian
Hank Hill
Powerpuff Girls ***NEW****
Ed Edd n Eddy ***NEW***
Kenny
Cartman
Stan
Kyle
Butters ****NEW***
Shrek
Garfield
Pinkie Pie
Twilight Sparkle ****NEW****
Ronald Mcdonald
Strong Bad
Homestar
The Cheat
Pico
Nene
Darnell
The Boyfriend ***NEW****
Tankman
Alien Hominid
Angry Faic
Crewmate ****New****
Salad Fingers
Stick Dude
Red Stick Dude ***NEW****
Red Ball
Dot of Excellence
Dottette
Red Dot
Blue Dot
Pencil
Nerd
Bar of Soap
Wegra
Penis
Tits
Turd
Brain
Scribble
Wtf?
O RLY
Hippyspop (OC) ****NEW****
Recycle Bin
DLC Pack 1
Returning:
Rouge
Alucard
Salt and Pepper Shakers
Ninja Kitten
Zeeky Bomb
Pube Muppet
Doug Funny
Wade Fulp
Tom Fulp
Newcomers:
Bert and Ernie
Nostalgia Critic
Orange Clock
A Chicken
King Harkinian
Shaggy and Scooby
Wolverine
Edd (Eddsworld)
Charlie & Pim