Get your Free Lego Monster Keychain. Just visit any Lego stores on 10/31 in your Halloween costume to get this freebie. This freebie offer is good while supplies last.
From their site: Visit the LEGO Store on Halloween dressed in your Halloween costume and get a free LEGO Monster Fighters The Monster Key Chain, while supplies last! Only valid on item #850453. Offer valid only at the LEGO Store on October 31, 2013 while supplies last.