Instructions
'Snagging'
Engage in a battle with any trainer.
Attack any "shadow" Pokemon that appear in battle. These Pokemon have a purple shadow behind them. You can capture only shadow Pokemon.
Throw a Pokeball at a shadow Pokemon when its health is in the red zone. This is the way to obtain a shadow Pokemon. There are a total of 83 obtainable shadow Pokemon in the game. If you miss one, you can try to catch it again by battling Miror B.
Trading
Travel to Pyrite Town or Outskirt Stand. You can trade with two people in "Pokemon XD" to obtain new Pokemon.
Talk to Danny if you are in Outskirt Stand, or Duking if you are in Pyrite Town.
Trade a Togepi to Danny to receive an Elekid. Trade a Trapinch, Surskit or Wooper to Duking to receive a Meditite, a Shuckle or a Larvitar.
PokeSpots
Travel to any of the three PokeSpots in the game: Oasis, RockGround or Cave.
Deposit some PokeSnacks in the center of the PokeSpot. Leave the area.
Return to the area when you receive a "PokeSpot" alert on your PDA. Battle the wild Pokemon and capture it with a Pokeball.
Mt. Battle
Travel to Mt. Battle and defeat all of the trainers. This is a grueling challenge and you will need to have trained your Pokemon to a high level before you can complete it.
Choose between Chikorita, Totodile or Cyndaquil once you have completed Mt. Battle.
Repeat the Mt. Battle challenge two more times in order to receive the remaining two Pokemon.