You can only get Oak's Letter from a Nintendo event or via a cheating device. The event activates the Flower Paradise where Shaymin is at in-game.
No. The Shaymin event (oaks letter) in Pokemon platinum is not shareable. ~Bellafuzz
You can obtain it only through a official Nintendo event.
you can't. you can catch a shymin in platinum with oaks letter which you can get with an event.
you can only get oaks letter in Pokemon platinum by an event. if you have action replay, you could also get it from an event there.
You have to get it from an event, but there hasn't been any event lately for Pokemon diamond/pearl. Most of the events are for platinum now, oaks letter was given out a feew weeks ago for platinum. You can keep a look out though by going to serebii.net
Event or cheat
yes but you have to have oaks letter and that is an event item which you can no longer get
go to a Nintendo event.
oaks letter
take it to the rock up there by the Pokemon league
only with a event
u need oaks letter that's where shaymin is get oaks letter.