Actor Sacha Baron Cohen, right, as Bruno, one of his characters during a Yes on Prop. 8 rally, Sunday, Nov. 2, 2008 in Los Angeles. Photo Mark J. Terrill/AP.
The British comedian is working on a film based on the fictional character Bruno, a gay Austrian fashion reporter who conducted gag interviews on HBO's Da Ali G Show.
Cohen, in disguise in a blond wig and preppy outfit, marched with demonstrators who support Proposition 8 while being trailed by cameras in a rally across from City Hall.
When photographers and reporters realized who he was and tried to approach the star, members of his film crew tried to shield him, and he was eventually whisked away in a van.
Cohen, who has made a career out of filming unwitting victims of his fake identities, also played a journalist in the hit movie Borat: Cultural Learnings of America for Make Benefit Glorious Nation of Kazakhstan.