I read on a website (I'm pretty sure it was on Serebii) that if you have a GBA Pokemon game in your DS while you're in certain places in DPP that different Pokemon will come. Is it true, because I almost always play with my Sapphire in, and no new Pokemon came?
If you put in EMERALD, I know you can get the rare pokemon that are in the special area of the Safari Zone (Pineco, Teddiursa, etc.) I'm not sure about other versions, though.
I know this is a fairly old question, but this link gives exact details
Yep, certain version-exclusive Pokemon, such as Growlithe Vulpix, Caterpie, Weedle, Mawile, Sableye, and even Shuckle, will appear if you put in their respective game!