There are so many Pokémon to find in Brilliant Diamond and Shining Pearl that players will want to prioritize their wishlists from the very start of the game. For many, Shiny Pokémon will be one of the most important things that they try and find in the game.
Others will want to make a start on their Mythical collection by grabbing Mew and Jirachi as quickly as they can. You can get these by having saves from Let’s Go Pikachu/Eevee and Sword and Shield on your Switch. Before they do, they will want to know if those Pokémon can be Shiny. Sadly, both Mew and Jirachi are Shiny locked, so there is no point in manually saving and then reloading the encounter that gets you the Pokémon. No matter what you do, they will not be Shiny variants.
Manaphy is no more difficult to get. You will need to visit the TV building in Jubilife City and go to the third floor and speak with an NPC there to get access to Mystery Gifts, and you will receive a Manaphy Egg. Manaphy is also Shiny locked, so there is little reason to try and juke this in your favor either.
Now, keep in mind that it is still early days, and it may turn out that Shiny versions are available, but none have turned up at the moment and the really do appear to be Shiny locked.
