Just because i don't know the answer...

[FOUR=FOUR]

But how do you get Skyform Shaymin? Do you have to have Platinum?

[Nato potato]

1 yes u do need platinum
2 u need shaymin to hold a special item i think its called glacidia flower

[Alice!]

You need a Shaymin on a copy of Platinum. Once you have that, you can talk to a girl in Floaroma Town and obtain the Key Item called the Glacidia Flower. It's not something you have to attach; once you use it your Shaymin will always be in Sky Form.

Well, not always. Shaymin will revert to its Land Form between the hours of 8pm and 7am. Thus, you can only use Sky Form during the day. In addition, if the Sky Form is ever frozen, it will revert back to its Land Form for the duration of its freeze regardless of what time it is.

[FOUR=FOUR]

What happens if you transfer the Shaymin to Diamond or Pearl, or even My Pokemon Ranch for that matter? Will it just assume the appearance of a normal Shaymin on those games?

[Alice!]

If you transfer the Shaymin to Diamond or Pearl it just goes back to its Land Form and will reassume Sky Form when it comes back to Platinum. I'd assume it works the same for Pokemon Ranch.

[Operative #19]

Actually, I believe there is an update for My Pokemon Ranch that allows you to view the other forms of Giratina and Shaymin. I don't know if it's been released in the U.S., though.