>>35376302A few rules:
1) No Pokemon who can Mega-Evolve or have Regional Forms can be Fusion Pokemon.
2) Pokemon with alternate forms like Deerling, Shellos, or Gourgeist are not capable of Fusion unless with another version of their species. In case of Pokemon with multiple forms like Deerling there are specific combinations to fuse; Winter/Summer & Spring/Fall would work but Winter/Spring or Fall/Fall wouldn't work.
3) Starters can only fuse with Starters from other regions. Examples: Infernape/Emboar, Typhlosion/Delphox, Meganium/Serperior, Torterra/Chestnaught, Samurott/Empoleon, Greninja/Feraligator
4) Legendaries can only fuse with Legendaries that are on the same 'Level of Deification.' I define that as whether the Legend is part of a lesser Trio/Duo/Quartet (Cressalia/Darkrai, Tapus Lele/Fini), the Leader of a Trio (Regigigas/Keldeo), a major Box Legend (Lugia/Ho-oh, Palkia/Dialga), or a Mythical Pokemon (Jirachi/Marshadow, Genesect/Deoxis)