The Regional Variants Game

[ReKoil]

Relic Castle, causing the quicksand pits =3

Fennekin (Fairy)

 

[Starlight]

Roaming around the top of Mt. Coronet!

Psyduck (Psychic / Flying)

 

[VisionofMilotic]

Encounter while soaring, they spawn more frequently in flocks above Mossdeep city.

Teddiursa (dark)

 

[ReKoil]

For sale in the Game Corner for 9.999
When you buy it, it runs away first chance it gets and returns to the game corner to be put up for sale again. it's quite the racket!

Kingdra (Fairy/Water)

 

[Starlight]

Meteor Falls with the Super Rod if you have a Fairy Pokémon holding a water stone in your party :)

Jigglypuff (Rock) star

 

[ReKoil]

A gift from Roxie after you beat her gym! (I could not un-see or un-think Rockstar and gave in lol)

Bruxish (Ghost/Psychic)

 

[Starlight]

Your nightmares Found in the abandoned ship on route 108!

Wailord (Ice)

 

[ReKoil]

the Frigid Sea, just outside of player reach. There just to taunt you +_+

Breloom (Bug/Normal)

 

[Hyzenthlay]

Kalos Route 20, in the depths of woods where it's nice and dark!

Lapras (ghost/dragon)

 

[Eleanor]

Hoenn's Abandoned Ship!

Jumpluff (Flying/Steel)

 

[Roni]

How have I never seen this game until now

A Fuego Ironworks employee~

Chansey (Dark/Fighting)

 

[ReKoil]

Operating Po Town's Pokemon Center :fufu:

Komala (Ground)

 

[Roni]

Def Cinnabar Island in HGSS if you could encounter wild mons there :p

Tyrogue (Water)

 

[Orion☆]

Tohjo Falls!

Mimikyu (Ghost/Electric)

 

[Roni]

Gotta be either New Mauville or the Kanto Power Plant heh

Bruxish (Dragon/Fire)

 

[Devalue]

Fiery Path near Hoenn's Lavaridge Town. Used the town's hot springs as an intermediary.

Steelix (Steel/Dark)

 

[Orion☆]

The Giant Chasm in Unova or thereabouts. A prelude to the actual monster there.

Houndoom (Ghost/Fire)

 

[ReKoil]

Mount Pyre's secret basement of the damned
Patrolling the graves at the top perhaps?

Liepard (Psychic/Ghost)

 

[Devalue]

Route 7 in Kalos (the area with the daycare). Stalks a Pokemon very weak to it for sustenance: Croagunk. May also be for revenge in their original life too.

Beartic (Water/Fighting)

 

[NoFreddyInWork]

I think it will be
Route 3 just by walking in the tall grass hopeing for one
It will just a poor Nidoran (m) being there wanting for it's trainer
Nidoran (m)
Steel/dragon