Inside the Oscar After Parties: Kate Hudson Plans Dance Party With Leonardo DiCaprio and Taylor Swift Hangs Wi

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Once the Oscars have been passed out, it's time for an outfit change and an after party!

ET got into some of the most exclusive, invite-only events over the weekend and saw how the stars were celebrating when the cameras were off and the drinks were poured.

WATCH: Gwen Stefani Wears Sexy Sheer Dress for First Red Carpet Appearance With Blake Shelton

From Elton John and David Furnish's annual bash to Vanity Fair's style-savvy soiree, here's a look at how celebrities let loose on Hollywood's biggest night.

Vanity Fair Oscar Party

Kate Hudson was ready to party when she showed up in a super sexy metallic gown to the event, which was catered by chef Thomas Keller of Bouchon. The actress was very excited for Leonardo DiCaprio's big win and joked with ET that she wanted to start a dance party with The Revenant   actor.

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Taylor Swift's squad at the event included her brother Austin and "Royals" singer Lorde. The GRAMMY winner was also spotted chatting with Nick Jonas, who coincidentally was at the same event as his current rumored love interest, Hudson. Nick and Taylor had an intense conversation, after which the singer left with Taylor and her party.

Oscar winner Alicia Vikander was spotted talking to True Blood star and fellow Swedish actor, Alexander Skarsgård. The Danish Girl actress instructed her friend not to leave without telling her and boyfriend Michael Fassbender. The two were acting very sweet and displaying PDA, with Michael giving Alicia a big kiss before she walked the carpet.

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It appeared to be a double date night for Demi Lovato and Wilmer Valderrama, who were seen hanging out with Justin Timberlake and his wife, Jessica Biel, who seemed to have a particularly intense conversation with Valderrama during their time together. Later in the evening, Biel and Timberlake were spotted leaving the party hand in hand.

After her emotional performance at the Oscars, Lady Gaga took court as she camped out on a sofa and was greeted by her peers. Music legend Quincy Jones was seated with Gaga, and at one point, Adrien Brody came over to snap a selfie with the pop star. In fact, Gaga enjoyed quite a bit of attention throughout the night. There was even a receiving line for people waiting to be in the presence of Mother Monster.

Newlyweds Jimmy Iovine and Liberty Ross
were also at the party and the model's dress looked a little familiar. Ross wore a vintage Dior gown to the event, which just so happened to be look a whole lot like her wedding dress! The couple posed with Mary J. Blige, who sang a few weeks earlier at their wedding. The R&B singer told ET that her favorite part of the "fairy tale" ceremony was singing Ross down the aisle.

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The last to leave? Rachel McAdams! The Spotlight actress wasn’t seen stepping out from the party until 3 a.m.!

PHOTOS: Kate Winslet's Tearful Reaction to Leonardo DiCaprio's Oscar Win Will Give You All the Feels

24th annual Elton John AIDS Foundation's Oscar Viewing Party

Everyone from Caitlyn Jenner to Vince Vaughn were at this bash, which raised $6.2 million to aid in the fight against HIV/AIDS. Jenner didn't stay too long -- she also stopped by the Vanity Fair party -- but was friendly with photographers as she exited the party. Meanwhile, Vaughn stuck around and appeared to be on drink duty, as he continued to go up the bar and bring beverages back to his group.

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Newly single Lea Michele was also there and told ET that she is "feeling strong" after her breakup and is focused on bringing peace and happiness into her life.

Michele's Scream Queens co-star, Glen Powell, showed up to the party and dished to ET that he had spoken with the show's creator, Ryan Murphy, and fans can expect an "insane" season two.

Oscar winner Hilary Swank was escorted to the party by her boyfriend, Ruben Torres. The two were super friendly when a fan asked for a photo with the "Million Dollar Baby" star.

Meanwhile, Dave Grohl was happily dancing to Elton John's greatest hits and twirling a few of his gal pals near his table.

Charlie Sheen showed up with a message to promote. The former Two and a Half Men star -- who revealed last year that he is HIV-positive -- was wearing a T-shirt with his face on it and the message: "Stay positively negative." He told ET that the shirts are on sale and proceeds will go to benefit AIDS charities.

ET got a big beauty reveal out of actress Retta, who admitted that she did her own makeup and hair for the event. The Parks and Recreation star, Straight Outta Compton's Aldis Hodge and Russell Simmons also all praised Chris Rock for his Oscars monologue.

Actress Brittany Snow was seen going above and beyond for a fan. The Pitch Perfect 2 star snapped photos in the hall with an admirer and even stopped to chat and introduce herself after the impromptu photo shoot.

WATCH: The Oscars' Best, Worst & Weirdest Moments: Long-Awaited Wins, Surprising Upsets and Failed Jokes

Other Star Sightings

Julianne Moore and Mark Ruffalo had a Kids Are Alright reunion at the Sunset Tower Hotel, and also hung out with Olivia Munn and her beau, Aaron Rodgers. Moore was joined by her husband, Bart Freundlich, and Ruffalo had his wife, Sunrise Coigney, by his side. Munn was a little late to the triple date as she did a wardrobe change before hitting the town.

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While most stars partied after the Oscars (including Jennifer Garner), Ben Affleck and Matt Damon showed up on Jimmy Kimmel Live. See how The Martian star managed to maneuver his way onto the late show set after Kimmel vowed never to have the actor on as a guest.

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