It's been weeks since the star-studded birthday party of Ellen DeGeneres, but there are still incredible stories pouring in from the A-list guests.

Take Oprah Winfrey, who was having so much fun that she didn't even recognize the famous leading man she was talking to at the bash.

"I can't remember in my life having that much fun," Winfrey says during her appearance at The Ellen Show. She emphasizes, "In my life!"

Oprah Completely Misses Leo's Identity

The Oprah Winfrey Network host explains that she knows a lot of celebrities from her show throughout the years. However, she stresses, when they do show up for an appearance at her show, they look like how they do onscreen.

At the DeGeneres birthday bash, the guests apparently came "in disguise," looking more like regular people. Besides, Oprah points out, she's a homebody who doesn't really go out a lot.

"This guy passes by," Winfrey says, adding that he asked her how she's been and began to engage her in small talk. The talk show icon, who was talking to The Weeknd at the time, didn't have a clue who she was talking to.

"So this guy comes back and I'm thinking, 'I know it's somebody, I know it's somebody, who is it?'" she continues. "Is it Justin Timberlake? I don't think it's Justin Timberlake."

Fortunately, The Weeknd didn't have the same problem identifying the A-list star, telling him that he loved one of his films. When the mystery guest responded that it wasn't his favorite out of his filmography, Winfrey jumped at the chance to figure out who he was.

"I go, 'So what was your favorite film?' And he says, 'The Aviator,'" Winfrey recounts that it finally clicked who the actor was: Oscar winner Leonardo DiCaprio. "And I say, 'Leonardo, you're so funny!'"

The Weeknd even captured the conversation between the trio on his Instagram page.

A post shared by The Weeknd (@theweeknd) on Feb 12, 2018 at 5:20pm PST

Despite the awkward encounter, Winfrey tells DeGeneres that the party was the most fun she's ever had. One particular highlight is the diversity of the people who attended the event, all from different backgrounds and industries.

Possibly The Best Party Ever

So many iconic moments took place at DeGeneres' 60th birthday party, including Kim Kardashian West posing for a photo with husband, Kanye West, John Legend, and Chrissy Teigen.

Other A-list Hollywood stars also showed up such as Jennifer Aniston, Jennifer Lawrence, Adele, Reese Witherspoon, and many more.

Witherspoon gathered all of the music industry guest and encouraged them to get onstage, which led to performances by Pharrell Williams, French Montana, Pink, Alessia Cara, and Melissa Etheridge.

David Spade, who was passed a medical marijuana at the bash, was nearly as confused as Winfrey, mistaking DeGeneres for Justin Bieber for the first hour of being there.