From a February 19 Washington Independent article by David Weigel, who reports that he spoke to Hannah Giles at CPAC 2010:

I asked Giles about a criticism that's often been leveled against them -- that they hyped up the video by wearing outrageous clothes in promotional materials and the videos' introductions that they didn't wear in the actual stings.

“We never claimed that he went in with a pimp costume,” said Giles. “That was b-roll. It was purely b-roll. He was a pimp, I was a prostitute, and we were walking in front of government buildings to show how the government was whoring out the American people.”

In fact, in a Sept. 21, 2009 Washington Times column, Andrew Breitbart wrote [emphasis added]:

When filmmaker and provocateur James O'Keefe came to my office to show me the video of him and his friend, Hannah Giles, going to the Baltimore offices of ACORN - the nation's foremost “community organizers” - dressed as a pimp and a prostitute and asking for - and getting - help for various illegal activities, he sought my advice.