Evolve your pokemon them it will turn to it original name. To change the nickname go to the Name Rater in Eterna City. If you can't change the name, the Pokemon is probably traded. If you want to change the name of a traded Pokemon, trade it back to it's original game and change the name.
You cannot change the name of a Pokemon that you did not originally catch or hatch.
It was probably traded
Pokemon games, including Pokemon Diamond Version, have always included a feature that allows you to nickname your Pokemon even after you have already decided on it's name. If you have named a Pokemon and wish to change that name, look no further than a man called the Name Rater. First, he will ask you whitch Pokemon you want him to look at. Then, he'll make comments on your Pokemon's name, and ask you if you want to change it. Then, if you want to, you can reply "yes" and think of a new name for the chosen Pokemon. If you are playing Pokemon Diamond, Pearl or Platinum versions, then you will want Sinnoh's Name Rater, as there is one in every game (excluding the Mystery Dungeon series - There is no way to rename a Pokemon in these games.) Sinnoh's top name-replacing guy can be found in Eterna City. Note; in Pokemon Black and White Versions, you will be informed of all the attractions and services in a city when you hover the cursor over it on the map. When hovering above Castelia City, you will see the subtitle "Name Rating Services."
There are some action replay codes to change your name to Dialga and a couple that have concequences and your name changes to ???? but other than that I don't think you can change it after you start a new game.
Evolve your pokemon them it will turn to it original name. To change the nickname go to the Name Rater in Eterna City. If you can't change the name, the Pokemon is probably traded. If you want to change the name of a traded Pokemon, trade it back to it's original game and change the name.
You cannot change a pokemon's nickname
Pokemon*Said with a French accent
The Name Rater in a house in Lavender Town can change your non-traded Pokemon's nickname.
Find the name rater.
On every Pokemon game, there is a name changer. He will allow you to change your Pokemon's name, either with a small fee, or free of charge.
Some where there is a guy that you ask then he will change the Pokemon's name, he is in a house some where.
if you wanna change your name make a new pokemon crystal or go on settings
In Castelia City you can change your pokemons name. In the pokemon gym road of Castelia city there is a man in the lefthand building who will change your pokemons name. Just like in the previous games you can only change the names of captured pokemon. (Not traded pokemon, or pokemon labelled "N's Pokemon".)
Unfortunately there is no way to change the name of your human character once you have chosen it. To change the name of your Pokemon, the name rater should be in Goldenrod next to the Pokemart.
You can't, as with all traded Pokemon, you can't change their name.
You cannot change the name of a Pokemon that you did not originally catch or hatch.