Manaphy is a Mythical Pokemon, meaning it can only be obtained through special events or distribution methods. It was never available in the original Pokemon Diamond or Pearl games.
However, you can obtain Manaphy in Pokemon Brilliant Diamond and Shining Pearl through the following methods:
* Event Distribution: Nintendo sometimes distributes Manaphy through events. Keep an eye out for announcements about these events.
* Trading: If someone has a Manaphy from an event distribution, you can trade for it with them.
* Breeding: If you have a Manaphy from a previous game, you can breed it in Brilliant Diamond and Shining Pearl to get more Manaphy eggs.
Remember, there is no way to find a wild Manaphy in any Pokemon game, including Diamond, Brilliant Diamond, Pearl, and Shining Pearl.