...holy hell. Just a few minutes after I posted that, I logged onto the Global Terminal in Platinum and discovered that someone had accepted my offer of a Zapdos in trade for Spiritomb, which made me happy until I realized...

...this is Cynthia's Spiritomb.
Seriously, it's a L58 female Spiritomb who knows Dark Pulse, Psychic, Silver Wind and Shadow Ball, was caught by a Master Ball and is listed as having been met at L58 in Pokémon League. I think this "ANTOINE" used a Game Shark code that makes trainers' pokémon catchable.
I...I'm not sure what to do with this thing.