>>19120715http://www.serebii.net/games/deoxys.shtml"When you trade Deoxys from game to game, its stats and appearence change to the Stats and Appearence of that game. However Attacks, IV's and Effort Points stay the same. Say you put 129 EP's on Special Attack...trade over and even if the stat changes, the Effort Points stay the same as do the IV's which help determine the stats. So If you trade Attack Deoxys to Colosseum...it'll be Normal Form, to Emerald...it'll be Speed Forme
So if you're training a specific Deoxys it has to be on the particular game. However you can trade it to get attacks that it cannot normally learn like getting an Attack Deoxys with Extremespeed or a Speed one with Hyper Beam
They are perfectly usable in Link Battles. However in the third generation, there is a snag to doing this, when Battling lets say FireRed to LeafGreen both with Deoxys. The following will happen:
First, on your opponent's screen, no matter what game you are using or what form you are using, it will look like a Normal form. However, the stats for the Deoxys would equal the game so if one person is using an Attack Deoxys...it will stay as one stat wise, even if someone is using Defense Deoxys in battle against you...It would truely be Attack Deoxys VS Defense Deoxys...you just would be unable to see it. This even happens on Pokémon Colosseum"
Do you want me to dig out similar sources on gen 4 and gen 5, because I'm sure I can find them