Organizers of Hollywood's biggest night are white-knuckled as they brace for more tales of the unexpected that could anger viewers or throw the finely-calibrated global telecast off schedule.

But the raw emotion and the unscripted moments are also what makes Oscars night memorable.

With a global television audience in the billions, the temptation to use Oscars night as a platform for making political statements has proved irresistible throughout the years.

Taking a swipe at critics who say Hollywood is out of touch, Oscar-winner George Clooney in 2006 noted that movie makers had crusaded for civil rights and against AIDS long before the issues became popular.

"I'm proud to be out of touch," Clooney said.

As statements go, it was on the mild side.

Three years earlier, boos rang out around the auditorium when maverick filmmaker Michael Moore launched a vitriolic attack on US President George W Bush for waging war in Iraq.

But Moore was only following the tradition of turning the winners podium into a pulpit.

Arguably the most famous example of that came in 1973, when a woman calling herself Sacheen Littlefeather stood before the stunned audience to collect Marlon Brando's best actor Oscar for The Godfather.

Littlefeather promptly refused to collect the award on Brando's behalf to protest the movie industry's treatment of Native Americans.

Four years later, Vanessa Redgrave drew gasps and boos from the Oscars faithful when she thanked the Academy for honoring her in Julia despite "the threats of a small bunch of Zionist hoodlums."

In the same awards ceremony, Oscars presenter Paddy Chayefsky chastised her to much applause: "I am sick and tired of people exploiting the Academy Awards for the propagation of their own personal propaganda.

"I would like to suggest to Miss Redgrave that her winning an Academy Award is not a pivotal moment in history, does not require a proclamation, and a simple 'Thank you' would have sufficed."

Sometimes, who the awards are given to can stoke controversy.

The decision to grant director Elia Kazan a lifetime achievement award in 1999 divided the glitterati, with dozens of stars refusing to rise or applaud, in protest at the film maker's decision to co-operate with the authorities during the 1950s communist witch-hunts.

Politics aside, Oscars night has been littered with memorable one-offs.

In 1974 a naked man invaded the stage as actor David Niven was hosting the show, prompting him to quip: "The only laugh that man will ever get in his life is by stripping ... and showing his shortcomings."

More recently, in 2003 actor Adrien Brody stunned viewers and superstar Halle Berry by kissing her passionately on the lips as she presented his best actor statuette, creating an Oscars signature moment.