Start/End Dates	2012-05-07 through 2012-05-31
Country	Japan

Details

The official Japanese Pokémon website announced that there would be a distribution of four Pokémon as part of the Powerful Tag Pokémon (強力タッグポケモン) campaign at the Pokémon Centers. From May 7th, 2012 until May 31st, 2012, players of the Japanese version of Pokémon Black and White could receive Kyukon (キュウコン) and Chandela (シャンデラ). From June 1st, 2012 until June 22nd, 2012 players could also receive Lucario (ルカリオ) and Elphoon (エルフーン). Below are the full details for each Pokémon.

Chandela (シャンデラ)

Pokémon Smash 86

In Pokémon Smash 86, it was announced that the first part of the Powerful Tag Pokémon (強力タッグポケモン) campaign at the Pokémon Centers would be ending shortly and Kyukon (キュウコン) and Chandela (シャンデラ) would be replaced with Lucario (ルカリオ) and Elphoon (エルフーン).


Source: http://www.pokemon.co.jp/info/2012/04/120427_p01.html