I've been so bored of late that I started writing a roster of characters for a what if scenario of Nintendo having just as much presence in a X zone title as the other 3 companies.
Pair units:
Claude and Dimitri
Samus and Captain falcon
Rex and Pyra
Pit and Valkirye
Solo units:
Dark Pit
Isaac
Tsubasa
Zelda
I imagine Dark Pit being like Heihachi and Segata where they are introduced as boss characters but when you beat them they properly join the party.
Isaac is there because X zone tend to have retro niche characters as solo units and Tsubasa is there because she's both a Nintendo character and a Sega character so it fits.
I remember thinking of ideas for that scenario as well, here’s what I had before:
Pair Units
Legend of Zelda: Zelda & Impa
Kid Icarus: Pit and Dark Pit
Shin Onigashima Kouhen: Donbe & Hikari
Kaeru no Tame ni Kane wa Naru: Prince of Sablé
Fire Emblem: Eliwood and Hector, Alm & Celica,
Sin & Punishment: Saki and Airan
Golden Sun: Isaac and Felix
Zangeki no Reginleiv: Frey and Freya
Xenoblade Chronicles: Rex & Pyra, Nia & Dromarch,
ARMS: Spring Man and Ribbon Girl
Solo Units
Legend of Zelda: Link (uses Navi to communicate)
Metroid: Samus Aran
Punch Out: Little Mac (uses Doc Louis to communicate)
Kid Icarus: Magnus, Phosphora
The Mysterious Murasame Castle: Takamaru
Advance Wars: Andy
F-Zero: Captain Falcon
Fire Emblem: Marth, Ike, Tiki, Lyn
Custom Robo: Ray MK III
Captain Rainbow: Captain Rainbow
Xenoblade Chronicles: Elma