The backstage farce "Birdman" topped the 21st annual Screen Actors Guild Award, winning best ensemble cast, even though its star, Micheal Keaton, was upset by Eddie Redmayne in the most outstanding actor category.

Oscar favorites Julianne Moore, Patricia Arquette and J.K. Simmons cemented their front-runner status in a ceremony that often serves as a kind of preview to the Academy Awards.

Redmayne, who stars as Stephen Hawking in "The Theory of Everything," was the somewhat surprise winner in a category expected to go to Keaton for his career-capping performance as a Hollywood has-been trying to mount a comeback on Broadway. Redmayne dedicated his award — "this very wonderful skinny man" — to sufferers and victims of ALS.

Moore, widely considered the best-actress favorite, won most supporting actress for "Still Alice," in which she plays an academic with early onset Alzehimer's Disease.

Accepting the award for most outstanding supporting actor for his performance as a domineering jazz teacher in "Whiplash," Simmons thanked all 49 actors who appear in the drama.

"All of us actors are supporting actors," said Simmons, a veteran character actor. "Each of us is essential, completely crucial to the story because if there's one false moment, the train comes off the rails."

"Boyhood" star Patricia Arquette added the latest in a string of awards Sunday, taking the supporting actress honor for her performance, filmed over the course of 12 years.

"I can't tell you what this means to me," said Arquette. "I'm a fourth-generation actor. My family has been committed to acting for over a century, through feast or famine."

Sunday's show kicked things off with a pair of wins for the Netflix prison series "Orange Is the New Black," honoring it as best ensemble in a comedy and naming Uza Abuda most outstanding actress in a comedy series. Abuda won over a number of veteran stars, including Julia Louis-Dreyfus ("Veep") and Edie Falco ("Nurse Jackie").

Best ensemble cast in a drama series went to "Downton Abbey," the second time the series has won the category.

On Saturday night, Alejandro Gonzalez Inarritu's "Birdman" took the top award from the Producers Guild Awards, suggesting it may be formidable competition to the perceived front-runner, Richard Linklater's "Boyhood." The last seven PGA winners have also won best picture at the Academy Awards.

Because actors make up the largest portion of the Academy of Motion Pictures Arts and Sciences, the SAG Awards are also considered one of the most telling Oscar previews. Individually acting winners usually mirror each other exactly, or very nearly. Last year, the top four winners — Matthew McConaughey, Cate Blanchett, Lupita Nyong'o, Jared Leto — all went on to win Academy Awards after first scooping up SAG awards.

The predictive powers of the SAGs have been more checkered in matching its top award with eventual best-picture Oscar winners. In the last six years, SAG best-ensemble and Academy Award best-picture winners have lined up three times ("Argo," ''The King's Speech" and "Slumdog Millionaire"), while diverging just as often. Last year, the actors chose "American Hustle" over eventual Oscar winner "12 Years a Slave"; in 2011, they picked "The Help" over "The Artist"; and in 2009, "Inglourious Basterds" defeated "The Hurt Locker."

Two actors who usually reside on the big screen won the SAG awards for performances in a miniseries or TV movie: Mark Ruffalo (for HBO's "A Normal Heart") and Frances McDormand (for HBO's "Olive Kitteredge"). Kevin Spacey ("House of Cards"), William H. Macy ("Shameless") and Viola Davis ("How to Get Away With Murder") also collected awards.

Davis thanked the producers of the legal dram "for thinking that a sexualized, messy, mysterious woman could be a 49-year-old, dark-skinned African American woman who looks me."

Debbie Reynolds, the "Singin' in the Rain" star, was honored with the SAG lifetime achievement award, which her daughter, Carrie Fischer, presented. The 82-year-old Reynolds embarrassed Fischer with a story, recalling that her bun in the famous musical led her to warn her daughter ahead of playing Princess Leia in "Star Wars."

"I said, 'Well, Carrie, be careful of any weird hairdos,'" said Reynolds. "So luckily George gave her two buns."

She also remembered 1964's "The Unsinkable Molly Brown."

"In that movie I got to sing a wonderful song 'I Ain't Down Yet,'" said Reynolds. "Well, I ain't."