The Office Season 7 Episode 6 (The Office s07e06) with title “Costume Contest” aired on Thursday, October 28th 2010 at 09:00 pm via NBC Network.
Here is summary for The Office Season 7 Episode 6 :

When Darryl takes an idea to corporate over his head, Michael freaks out. Everyone in the office is in a competitive mood as the Halloweencostume contest gets underway. Meanwhile, Pam tries to get the truth out of Danny about their dating history.