From Bulbapedia, the community-driven Pokémon encyclopedia.
A diploma given after finishing the Sinnoh Pokédex (Pokémon Platinum).
The Diploma is an item received by completing a regional Pokédex. It is typically given by a Game Freak employee in the game. The diploma is not an item in the regular sense as it is not added to the player's inventory. To view it the player must talk to the person that originally gave them the diploma. The event Pokémon (Mew, Celebi, Jirachi, Deoxys, and Manaphy) are still not required to qualify for the diploma. In Generation IV, only seeing all the Sinnoh Pokémon will earn the diploma.
A separate diploma will be given for completing the National Dex in Generation III and beyond. The event Pokémon (Mew, Celebi, Jirachi, Deoxys, Manaphy, Phione, Darkrai, Shaymin and Arceus) are not required. Furthermore, unlike in Generation II, Lugia and Ho-Oh are regarded as event Pokémon in all games but Pokémon Ruby and Sapphire, and as such are not counted towards obtaining the diploma in those games.
In Pokémon Red and Green, it was long rumored that the player could obtain Mew from Game Freak's lead developer in Celadon Mansion after completing the Pokédex of 150 Pokémon. However, this is false; instead, a diploma is awarded for finishing the Pokédex.
Locations of diploma
Generation I/Generation II/FireRed and LeafGreen
In Generation I and Generation II along with Pokémon FireRed and LeafGreen, the diploma is given to the player in Celadon Mansion by Game Freak's lead developer.
In Pokémon Ruby, Sapphire, and Emerald, the diploma can be found in Cove Lily Motel, also by Game Freak's lead developer.
In Pokémon Diamond, Pearl, and Platinum, the diploma is found in the top left house of the Hotel Grand Lake on Route 213 by another of Game Freak's lead developers.
Pokémon Diamond and Pearl (Regional)
Diamond National Diploma.png
Pokémon Diamond and Pearl (National)
Pokémon Platinum (Regional)