So this turned out to be true.   Here are the deets on the video shoot:

"An unnamed source told the magazine that Spears had a "small part" in the video, which was shot Wednesday in Los Angeles. A "set source" told UsMagazine.com that Spears does not interact with the group in the video, and shot her scenes at the Warner Bros. lot Wednesday while the Dolls filmed in Hollywood.

"In the scene shot [Wednesday], Britney is driving in a car," the source said. "They all wave at each other as they are passing in traffic — that is it. Of course, Britney looks hot and blonde. It is a very short sequence, but [Britney] had a lot of fun with it. Britney really likes the Dolls' music and when she saw them on the MTV [Movie Awards], she was totally down to do the video."

She looked hot and blonde? 

This comes to mind: