Mario: Dr. Mario/Paper Mario/Strikers Charged gear
Luigi: Mr. L/Urban Champion/Strikers Charged gear
Peach: Daisy/Rosalina/Strikers Charged gear
Bowser: Bone Bowser (from NSMB)/Old-School Bowser (all green and no hair)/Strikers Charged gear
DK: Funky Kong/Kiddy Kong/Strikers Charged gear
Diddy Kong: Dixie Kong/Tiny Kong
Yoshi: Boshi/Birdo
Link: OoT Link/Zora Armor/Ordon Clothes
Zelda: OoT Zelda/WW Zelda/Robed Zelda
Sheik: OoT Sheik/Tetra/Impa (OoT)
Ganondorf: OoT Ganondorf/WW Ganondorf/Old-School Ganon (pig-man design from LoZ)
Toon Link: OoT Young Link/Old-School Link (based on Link's original design from LoZ)
Samus: Power Suit/Fusion Suit/Dark Suit/Light Suit/PED Suit/Any of the Hunters
Zamus: Justin Bailey/Bikini
Pit: Palutena/Old-School Pit (like his trophy in SSBM)
Ice Climbers: Balloon Fighter/Bubbles (Clu Clu Land)
ROB: ROB64/SPOILER AHEAD ->>
Kirby: Scarfy/Gooey
Meta Knight: Any of the Meta-Knights/Sword Knight/Blade Knight
Dedede: Rick (with a hammer)
Olimar: Louie
Fox: Peppy/Slippy/Assault Fox
Falco: Krystal/Assault Falco
Wolf: Leon/Panther/Assault Wolf
Captain Falcon: Black Shadow/Blood Falcon/Any other F-ZERO racer
Pikachu: Pichu/Raichi/Pachirisu
Pokemon Trainer: Blue/Green/Yellow/Gold/Silver/Kris/Ruby/Sapphire/Wally/Diamond/Pearl/Berlitz/any other Trainer/Gym Leader/Elite 4
Lucario: Mewtwo
Jigglypuff: Igglybuff/Wigglytuff
Marth: Sigurd/Celice/Leif
Ike: Roy/Eliwood/Ephraim
Ness: Paula/Poo/Ninten
Lucas: Kumatora/Claus (Masked Man)
Mr. Game & Watch: Mrs. Game & Watch, Sherrif
Snake: Liquid Snake/Raiden/Naked Snake/Old Snake
Sonic: Shadow/Knuckles/Mighty
I tried to get three costumes per character, but some (like G&W) just don't have the source material.