When Pokèmon Platinum was announced, lots of scans and screens came out on the net and Nintendo also put online a website about the game, with a screen of the battle vs. Giratina Origin. Howerer, the Giratina Origin sprite that we see in this screen is not the same one as the final version.
Also, there was a beta sprite of Shaymin Sky form that was dropped before the release. There are also some beta items in Platinum that are also in D/P:
- S.S. Ticket = A ticket for sailing with the S.S. Anne (but there’s no S.S. Anne in D/P/P!)
- Contest pass = A pass for entering the Pokèmon Contest (contests do not need a ticket)
- Magma Rock = A magma rock from the stark mountain (proupose unknown,maybe has something to do with Hetran)
- Red Chain = A chain created by the Lake Trio (even if it’s used by Cyrus for awakening Dialga/Palkia in the game,the proupose of this item is unknown)
- Rule Book = A book that contains the rules of the Wi-Fi mode (the rules in the Wi-Fi mode are writed into the instruction book)
- Seal Bag = A bag that can contain 10 seals (replaced with the Seal Case)
- Treasure Sack = A sack that holds the treasures found in the underground (replaced with the Special Selections for the underground)
They have no function in the game but they can be found by hacking the game or cheating.
(Source : Bulbapedia)
Another thing just discovered : Pokèmon Platinum has a test music that’s just a remix of the Pokèmon R/S/E opening. Howerer, the music is unused in the game.
Update: most of the Pokemon Gold and Silver references could be used in the new G/S remakes, since it’s intended to be compatible with Diamond, Pearl, and Platinum.