Pokémon Centers in Japan are offering a level 10 Nyarth for Pokemon Diamond, Pearl or Platinum players from March 20th to April 12th 2009. People that raise their Nyarth to level 30 and bring it back to a Pokémon Centers between April 18 - Thursday, April 30 can receive "Nyarth LCD cleaner" for free!

Below is information about the Nyarth:
Name: ニャース (Nyarth), Level: 10, Item: Amulet Coin, OT: オーサカ (OSAKA), ID: 03209, Ball: Cherish Ball, Moves: Fake Out, Pay Day, Assist, Scratch

You can also click on the poster for a higher resolution scan.

Source: http://www.pokemon.co.jp/info/pokemon/p090306_01.html/p090306_01.html