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Some of the movie world's biggest stars will be walking the red carpet at this year's Oscars in Los Angeles later.

Joker leads the pack with 11 nominations, followed by The Irishman, 1917 and Once Upon a Time in Hollywood with 10 each.

Brad Pitt, Renee Zellweger, Joaquin Phoenix and Laura Dern are among those tipped to win acting awards.

Sir Sam Mendes' World War One epic 1917 and South Korea's Parasite are the frontrunners to be named best picture.

Here are 12 things to look out for at Sunday's ceremony.

1. Brad Pitt winning his first acting Oscar (and making a funny speech)

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If you believe the experts, Pitt is going to win best supporting actor for Quentin Tarantino's Once Upon a Time in Hollywood.

If he does, the ever-popular star is likely to get one of the biggest ovations of the night.

He won an Oscar in 2014 for producing 12 Years a Slave, but his previous acting nominations - for Twelve Monkeys, The Curious Case of Benjamin Button and Moneyball - have all been unsuccessful.

He has swept this season's pre-Oscars awards - and, if it was possible, has won even more fans for the unfailingly witty and charming acceptance speeches at each one.

2. Joaquin Phoenix winning his first Oscar (and making a political speech)

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Phoenix is going to win best actor for his remarkable performance in Joker.

What's less predictable is what he will say at the podium, having used other recent acceptance speeches to send messages about climate change and "systemic racism" in the film industry.

"I think he will want to use that platform to say something useful," says Clarisse Loughrey, chief film critic for The Independent.

It will be the 45-year-old American's first Oscar win at his fourth attempt, after nominations for The Master, Gladiator and Walk the Line.

It's also hard to predict where he will go after the ceremony. After winning at the Screen Actors' Guild Awards in January, he swerved the after-parties and went to an animal rights protest outside an abattoir - still wearing his tux.

• Oscars 2020: Joker leads pack with 11 nominations

3. The Renéessance

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Renée Zellweger is going to win best actress for playing Judy Garland in Judy.

It will complete the comeback for an actress who was nominated for three years in a row from 2002-04, winning for Cold Mountain at her third attempt.

After that, she starred in a string of flops before stepping back from Hollywood - she has no IMDB credits between 2010 and 2016.

4. Any kind of shock

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Laura Dern is going to win best supporting actress for her role in Netflix divorce drama Marriage Story.

OK, there is normally some sort of surprise in the four acting categories, and that could well be the case this time, but most tipsters seem to believe Brad, Joaquin, Renee and Laura have them in the bag.

The closer races are in the other categories.

5. Sir Sam Mendes flying the flag

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The main British hope lies with Sir Sam's World War One epic 1917, which is among the frontrunners to win the top prize - best picture - while Sir Sam himself is a strong contender for best director.

However, the best picture and best director prizes have gone to the same films only twice in the past seven years. One of those was Birdman which, like 1917, was made to appear as if it was filmed in a single shot.

Sir Sam won best director in 2000 for American Beauty, and if he triumphs again it will be the biggest gap between two directing wins in Academy Awards history.

Roger Deakins, the British man who filmed 1917's "single" shot, is thought to be a dead cert to win best cinematography. After receiving 13 unsuccessful nominations, this would be his second Oscar in three years, after his 2018 triumph for Blade Runner 2049.

• Oscars 2020: The nominees in full

6. South Korea's Parasite making Oscars history

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If 1917 doesn't win best picture, the nearest competitor is thought to be South Korean drama Parasite, which has a lot of support to become the first non-English language movie to win the main award.

It tells the story of a poor South Korean family living in a tiny, dark semi-basement, and a wealthy family living in a glamorous home in Seoul.

• How Parasite got under the critics' skin ★★★★☆
• The real people living in a 'Parasite' basement

7. The host

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Actually, don't watch out for the host, because for the second year in a row there isn't one.

Last year, Tina Fey, Amy Poehler and Maya Rudolph delivered an opening monologue, but otherwise it was left to different celebrities to introduce each category.

8. Billie Eilish's Bond theme

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Not content with stealing the show at one award ceremony (sweeping the board at the Grammys), 18-year-old pop prodigy Billie Eilish will also perform at the Oscars.

There has been speculation that she will use the occasion to debut her theme tune for the new James Bond movie, No Time To Die.

But there has also been a suggestion that she could depart from her usual musical style and sing The Beatles' Yesterday to accompany the ceremony's In Memoriam segment.

9. A global choir of Elsas

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As usual, the best song nominees will be performed. They include Into The Unknown from Frozen II - which will be sung by no fewer than 10 Elsas.

Idina Menzel, who voices the animated character in the original version, will be joined on stage by actresses who provide the princess's voice for countries including Denmark, Japan, Poland, Russia, Spain and Thailand.

The other best song nominees include Sir Elton John for (I'm Gonna) Love Me Again from Rocketman; Erivo, who will perform Stand Up from Harriet; Randy Newman's I Can't Let You Throw Yourself Away from Toy Story 4; and Diane Warren for I'm Standing With You from Breakthrough.

Warren is another who is waiting for her first Oscar win, after 10 previous nods.

10. Kobe Bryant tribute

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As well as being an LA Lakers hero, Bryant, who died in a helicopter crash two weeks ago, won an Oscar in 2018 for a short animated film called Dear Basketball.

Oscar organisers have confirmed he will be in the In Memoriam section, but it's not known whether there will be a separate standalone tribute.

Kirk Douglas is also likely to be honoured after his death on Wednesday at the age of 103.

11. Any diversity

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It's likely (see above) that all four acting winners will be white. The only nominee who could change that is British star Cynthia Erivo, who's an outsider to win best actress for Harriet.

It's certain that the best director winner will be a man, after that category's nominees were all male for the ninth year out of the past 10. He could be South Korean (see above), however, if Bong Joon-Ho wins.

What has been remarked upon less is that there hasn't been a female winner of either of the screenplay awards for 12 years, since Diablo Cody's name was called for Juno in 2008.

This year, Greta Gerwig could break that run for her adaptation of Little Women, which might help make up for the fact she wasn't nominated for best director.

• Oscars 2020: How diverse are the nominations?
• Will Gompertz: My alternative Oscars shortlist

12. Keeping it in the family

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Little Women is also nominated for best picture - where its rivals include Marriage Story, made by her partner Noah Baumbach.

The couple, who have a child together, are also both nominated for their screenplays - although Gerwig is up for adapted screenplay while Baumbach is in the running for original screenplay.

Elsewhere, cousins Randy and Thomas Newman are going head-to-head in the best original score category for their work on Marriage Story and 1917 respectively.

Thomas has had 14 previous nominations without a win, while Randy has had 20 past nominations and two wins.

Also keeping it in the family are father and son Michael and Christian Minkler, who are nominated together for best sound mixing for Once Upon a Time in Hollywood.

Follow the red carpet, winners and reaction - live from 23:00 GMT on Sunday.

Before that, listen to BBC Radio 5 Live's special Oscars build-up show live from Hollywood from 20:00-22:00 GMT on Sunday.

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