Nope
Darkrai
No.
Sorry but there isn't a trainer with a bagon in platinum.
no one no trainer has a kingdra in Pokemon platinum exept for me :P
action replay
Darkrai.
Ok the answer is yes, but only throught the darkrai event
Darkrai is a Pokemon from Generation IV, and Pokemon ruby is a game from Generation III , so you can only get darkrai in Pokemon Platinum, Diamond or Pearl
You dont catch Darkrai in Pokemon Pearl. You can catch it in Pokemon Platinum at level 40.
No you don't have to.
In harbor inn
with a special event