User blog comment:Sekeagle/DLC 3rd party characters/@comment-26498136-20150707171602

Probable means that there's a chance (whether it be big or small), and improbable means that there's very little to no chance.

Mega Man (probable): Zero Mega Man (improbable): Proto Man, X

Final Fantasy (probable): Cloud Final Fanatsy (improbable): Kefka, Tidus

Ace Attorney (improbable): Phoenix Wright

Castlevania (probable): Simon Belmont Castlevania (improbable): Alucard

Pac-Man (improbable): Inky, Blinky, Pinky, Clyde