Wondercard Arceus:
Natures and IVs are randomly determined, yes. You can check your seed, in DPPt, by coinflip and in HGSS by calling elm. Abusing WC in HGSS is much easier though, since you can only check your seed in DPPt or get the pokemon and not both - reason being moving NPCs. HGSS yeah, too easy, haha. Just takes aloooot of times hitting your delays.