You can't really transform Pokemon, (accept with ditto) but when a certain Pokemon reaches a level, it turns into a stronger/bigger Pokemon. It's called evolution.
Unfortunately, Rotom does not transform in pokemon diamond, just in platinum, heartgold and soulsilver
it is a pokemon that can transform into any pokemon and you can find it in a route close by canlave city
you cant in dimand and pearl, but you can in platonom
you cant if its a regular Pokemon the original answerer is right but if it's a ditto and you are facing a legendary you can transform into it for the length of the battle or until ditto/legendary Pokemon faints if it faints during the battle.
If you mean transfrom Shaymin into Sky Forme, you cant. The only way to transform Shaymin into Sky Forme is to trade it into Pokemon Platinum which comes out in spring, March 22, 2009.You cannot transform Shaymin to its Sky Forme in Pokémon Diamond because its Sky Forme is not in the programming data and the item that it uses in order to change its Forme, the Gracidea is also not available in the programming data for Diamond.
Diamond doesn't have the coding programmed into it for Origin Forme, as it's likely the final design for it was made long after Diamond's release. Giratina can only be used as 'Altered Forme' in Diamond and Pearl.
Transform. 10 PP Then whatever moves the transformed Pokemon has (Only 5 PP of each move though)
all trainers i know u all have alot to accomplished good luck
Pokemon diamond
Pokemon diamond Pokemon diamond Pokemon diamond
no it is IMPOSSIBLE because the greiceous orb on pearl and diamond and it is the same with shaymin you cant get the gracedia flower either and there's no distortion world in diamond and pearl HOPE THIS HELPED!!!!!!!!!!!!!!!!!!!!!!!!!!-_- *_*
you cant be a Pokemon in Pokemon diamond