From Bulbapedia, the community-driven Pokémon encyclopedia.
WARNING: To those using this template, please only use this for Pokémon that legitimately appear in the wild in those games. For instance, Lunatone cannot be found in Emerald, so this does not apply to it. The only exception is for those for those in the Battle Pyramid and Battle Pike (Dusclops only). See here for details according to the Battle Pyramid. Please write it in the edit summary and write that it's possible only in the Battle Frontier with the parser Frontier.