Palkia (pearl only) Dialga (diamond only) Giratina (platnium,diamond or pearl) Rotom Uxie Mesprit Azelf Heatran Cresselia Manaphy (you need Pokemon ranger to get Manaphy)
definitely a Nintendo event
No, the only way is to attend a Nintendo event.
the Pokemon are pigey, mew2 first of all there are more than that and second pigey is not lengendary
You wait for a Nintendo Event that has the Azure Flute.
You go to a Nintendo Event or you can trade from a friend.
No.
You need a friend and go to the union room on the top of the Pokemon centers
You would have to go to a Nintendo event to get a certain item.
The most commonly missed Pokemon in the National Dex are Arceus, Darkrai and Shaymin. These are legendaries in Diamond and Pearl that cannot be caught without action replay or a Nintendo event. Recently there were Nintendo events for all three.
You can transfer it from an old Pokemon game (such as Pokemon fire red) or trade other people.
Without trading, cheating, or Nintendo events, you can get Dialga, Uxie, Azelf, Mesprit, Heatran, Giratina, and Cresselia.