Pokemon Platinum: How to Catch Shaymin
Q: Is Shaymin able to be caught by regular methods in Pokemon Platinum?
A: Unfortunately no, Shaymin can only be caught a couple of ways.
The first method is by attending an official Nintendo event, either by WiFi, or by going to an actual event where you can get special pokemon via wireless access points.
The event for Shaymin gives you an item called Oak’s Letter, which will allow you access to Flower Paradise where Shaymin is.
The only other method to catch Shaymin is to use the Action Replay system to catch him via cheating.
Alternatively you can trade him from the Diamond/Pearl versions, but I have heard rumors that both the Action Replay method and the trading method will keep him from being able to use his Sky form, which is only usable from the official event version.