@Michael Sypher When he first appeared in the previous Smash game, Cloud had also appeared in Theatrhythm Final Fantasy on 3DS. I think there have also been other Final Fantasy crossover things since then.
However, I think some of the spirits might have never been on a Nintendo system.
2B needs to be in a game that's on a Nintendo system in order to be in SSB. & before anybody says it, Cloud was in Kingdom Hearts games on GBA & DS, Joker will be in Persona Q2 for 3DS. They technically pass.