What item does professor oak give you in platinum I've talked to him at both were you get shaymin and at Pal Park and when i go to his house He says something about an item he got but itsaysbagisfull?

i don't really understand the Question format here, and since i ran out of characters in the question I'll explain here.

I've caught Shaymin, Darkrai, Cresselia,and Mesprit, Gotten the national dex, beaten the elite four and explored every city.

But when i go up to Oak in eterna City he says a friend from kanto sent him something and it looks like hes about to give it to me then it says Too bad: Bag is full

IF anyone knows what that item is and what it does please tell me this is frustrating

If you want a Shaymin, you need Oak's Letter (From an event or use Action Replay)

Then you travel to Route 224and you'll see a stone and it will ask you "Who do you thank on this adventure" or something like that, and put any answer. Then a path is made when you've written on the stone.

Go down the Path and at the end it will say Flower Paradise and you'll see shaymin.

To get Sky Forme Shaymin, go to Floroama Town and ask the blonde girl for some Gracidia flowers!

Hope I helped you!

I'm not sure, but could you just be talking about the dubious disc or whatever. That's the only thing I've received from Oak apart from the National dex.