>>33712892FRLG - Altering Cave in the Sevii Islands, but Altering Cave Pokémon are most likely not native Pokémon
Emerald - Altering Cave and the Safari Zone extension, neither are native to Hoenn
GSC - found in Kanto
HGSS - found in Kanto and the Johto Safari Zone (not native to Johto)
Pearl - breed Houndoom
Pearl (Houndoom) - Route 214 and 215 as Poké Radar encounters (are Poké Radar-exclusive Pokémon native?)
Platinum - Route 214 and Valor Lakefront as regular encounters
Black - swarming on Route 9 (are swarm-exclusive Pokémon native?)
X - Route 10
Gen I and III are the earliest points in the franchise, while Gen II and IV are three years later. BW is an unknown amount of time after that, B2W2 is two years after BW, and XY are concurrent with B2W2.
Houndour isn't a Pokémon native to Kanto (initially), Johto, or Hoenn. However, it does become native to Sinnoh in Platinum as a regular encounter. We just don't know if it was always a regular encounter. There's also always the possibility that it originally existed in Johto, but just died out and moved to Kanto, kinda like how Lickitung is found in Johto naturally but is a trade Pokémon in RG, Safari Zone Pokémon in Japanese Blue, Cerulean Cave in Yellow, and not in Kanto in Gen II.
>>33713033This is also a neat possibility.
