The new TV Anime Series Pocket Monsters Best Wishes Season 2 Episode N (ポケットモンスター ベストウイッシュ シーズン2 エピソードN) will begin on January 17th, 2013 and will feature the return of the Rocket Gang! To celebrate this, players of the Japanese version of Pocket Monsters Black 2 and White 2 will be able to download a Rocket Gang Nyarth. Nyarth has been in the anime series from the very start, more than 15 years, but this is the first time it is being offered as a present! Nyarth will be available for a limited time on the Nintendo Wi-Fi Connection from December 7th, 2012 until January 10th, 2013. Below are the full details.

Pokémon Info
Level: 15
Pokémon: Nyarth (ニャース)
OT: Rocket-dan (Rだん)
Poké ball: Cherish Ball (プレシャスボール)
Ability: Pickup (ものひろい)
Held Item: Smoke Ball (けむりだま)
Attack 1: Fury Swipes (みだれひっかき)
Attack 2: Sing (うたう)
Attack 3: Nasty Plot (わるだくみ)
Attack 4: Snatch (よこどり)

Source: http://www.pokemon.co.jp/info/2012/11/121130_g01.html