Hercules is the first Gym Leader of the game. He specializes in Fighting types.
Jessie and James are Team Rocket members they specialize in Poison types. Winning against one of them will make pokemon from other generations appear as well as pokemon from Alstra.
(if the player is Female)
(If the player is Male)
Eva is the third gym leader of the Alstra Region, she specializes in two types, depending on which version is played. If the player is using Pokemon Frostbite then she will use ghost pokemon, if they use Pokemon Sunburn then she will use Psychic types instead.