the next event is September 29, 2007 which is when manaphy can be downloaded. this manaphy you receive there is lvl 50 with heart swap already learned and comes within a cherish ball with a red scarf on kie in the movie
you only can get a mystery gift on Pokemon diamond and pearl
Nope, the only thing the Mystery Gift does is allow you to get event Pokemon
Mystery Gift event
you have to get mystery gift and go to a Nintendo event
With the Japanese event or mystery gift
Mystery gift is not really an item. You get Mystery gift and on the main menu you can select it. You can have 3 wonder cards (a card you receive when there is a Pokemon event.) I hope this answered your question
on certain days activate the mystery gift and you may get an event
you get it through Nintendo event or mystery gift on Pokemon pearl platinum or diamond
The only way to get Oak's Letter as a Mystery Gift was to wait for an event, go to that event, and then download it as a mystery gift. However, the event to get Shaymin in America for Diamond and Pearl has already passed, so it is impossible to get it as a mystery gift now. There has already been a Pokemon Event for Shaymin (what you need Oak's Letter for) for Pokemon Platinum, so that has passed, too.
Go to a Pokemon event.
There's an event right now in the US to get a Fatefully encountered Jirachi, go to mystery gift and select via Nintendo wi-fi
You have to go to a Nintendo event then they give you the member card. But, there hasn't been an event for that.