Isla Fisher: More Borat, Less Bruno

Sacha Baron Cohen's fiancee, Isla Fisher, will go to bed with Borat, the naive, instigative Kazakh reporter who exposed America as never before.

But refuses to sleep with one of Cohen's other comedic personas - the flamboyantly gay Austrian fashion reporter, Bruno.

Fisher, the Wedding Crashers star, agreed to endure Cohen staying in character as the lovable, yet anti-Semetic Kazakh reporter while he shot his hit film, Borat: Cultural Learnings of America for Make Benefit Glorious Nation of Kazakhstan.

However, she won't afford Cohen the same luxury he enjoyed as the Pamela Anderson-chasing horndog when he starts work on his forthcoming Bruno movie.

"Isla grudgingly endured months of living, and sleeping, with Borat when Sacha was making the movie as he had to stay in character while he was filming," a source close to the couple reveals.

"But now that he plans to make a Bruno movie, she says she absolutely won't let him stay in character 24 hours a day. She has issued an ultimatum: no Bruno in the bedroom or no sex until the film is finished."

Sasha Baron Cohen knows he's pushed his luck already.

After winning his Best Actor prize at the recent Golden Globe Awards, Cohen dedicated his triumph to Fisher because "she agreed to sleep with Borat for ten months."

Rumor has it that Isaac Cohen (no relation) recently issued an ultimatum to Britney Spears, insisting the pop princess stop going commando in public.