An upcoming distribution event will allow trainers to obtain the Pokemon Meloetta. This event will begin on March 4th, and will continue until March 24th. This distribution will be available at participating GameStop stores. All that is necessary to receive this Pokemon is a copy of Pokemon Black, Pokemon White, Pokemon Black 2, or Pokemon White 2 with fewer than 12 wonder cards attached to it. If there are 12 wonder cards attached to the game, it will be necessary to delete one. It will also be necessary to have any Nintendo DS or 3DS in order to run the game and connect to the distribution network.
This event will be the first time that Meloetta has been distributed in the United States. As such, this will be the first time trainers will be able to (legally) capture all 649 Pokemon without trading with trainers overseas.
Meloetta herself is a peculiar Pokemon. She has two forms, which can be changed at will during battle. This is done by using her signature move, Relic Song. Note that Meloetta does not learn this move by leveling up. In order to learn Relic Song, Meloetta must be taken to the cafe in one of the back alleys of Castelia City. There, a musician will teach her the move.
Meleotta begins battle in Aria form, and, after using Relic Song, she will transform into her Pirouette form. Changing form not only changes her appearance, but her stats and type as well. In Aria form, she is a Normal/Psychic-type Pokemon that specializes in Special Attack and Special Defense. In Pirouette form, she is a Normal/Fighting-type Pokemon that specializes in Attack and Defense. She is also quite a bit faster in Pirouette form. Due to the drastic differences in her forms, it is necessary to think ahead when selecting moves and training her if the trainer plans to use her for battle.
The link below leads to the official announcement from Pokemon.com.