I don't have Pokemon colosseum but I think I am going to have it on my..

1. On the game you can obtain only 60 different Pokemon, but using a Gameboy Advance - Gamecube Link Cable, you can trade any Pokemon you want from Emerald, Ruby, Sapphire, FireRed, or LeafGreen. But be careful, there is only three boxes in your PC on Colosseum, so you can only store 90 Pokemon at a time.
2. Theonly way you can get Pokemon in Colosseum is by stealing or 'snagging' an opponents Pokemon. But you can't take any Pokemon they have. You can only steal it if it is a Shadow Pokemon. If it is a Shadow Pokemon, your partner will point it out in battle and it will have a dark aura around it. If you catch one, you must return it to being a non-shadow Pokemon, by emptying it's Shadow Bar. You do this by letting it participate in battles, and calling it when it goes into 'Hyper Mode. When the shadow bar is empty, you can take the Pokemon to a certain place in the game, and it will be returned to normal, and declared yours to keep. Most of the Shadow Pokemon will be from the Johto region - numbers 152-250 (Gold, Silver, and Crystal Pokemon).
3. There are two modes in Colosseum. Story Mode, which I just explained to you, where you go on a classic Pokemon adventure, or Battle Mode, which is all-out battling. You do a bit of battling in Story Mode too, but not as much as Battle Mode. In Story Mode, all battles are 2 on 2, but in Battle Mode, you can choose either 1 on 1 or 2 on 2. I hope this helps. If you have any more questions, post them.

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2.pokemon that have a blocked heart
3.always