Wait, Who Are You? Amy Schumer, Justin Bieber, Miley Cyrus, More Stars Who Got Caught In Awkward Encounters With Other Celebs

Forgetting someone's name (or total existence) can be totally embarrassing for both parties, but what happens when Hollywood's hottest stars aren't recognized by their fellow celebrities? Let's just say things can get pretty awkward. 

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In 2017, Seinfeld's answer to a starstruck Kesha asking for a hug on the red carpet was a tense "No, thanks" — before he casually admitted, "I don't know who that was." Later asked about the on-camera dis, the comedian shrugged, "I'm 63… I don't know everyone." Fair enough!

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Robbie's clearly not the most devout royal watcher. Following a fancy bash, she copped to mistaking the prince for a fellow ginger Brit: "When I saw him in those glasses, I was like, 'Oh, I didn't know Ed Sheeran was at the party!' [Harry] got really offended. He was like, 'Shut up.'" Blame it on the beer goggles?

Before they established sparkling comedic chemistry as a mother-daughter pair in Snatched, Schumer spotted Hawn on a flight and pitched her the role — only to be politely brushed off as a random fan. "I feel bad every time I hear this story," Hawn's said. Yikes emoji, anyone?

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The Biebs has had plenty of time to make things up to his fellow Canadian pop star since a 2015 radio interview when he was pressed for advice for the up-and-coming crooner — and was forced to ask his publicist, "Who's Shawn Mendes?" Uh… just that future Grammy nominee over there.

Who wants a drive-by hug from a world-famous singer? On the Good Morning America set, Cyrus "came up and hugged me," recalled Mama June — who had no idea who she'd just embraced. "I didn't realize it was her until after she walked by!" What the twerk?!

BRITNEY SPEARS' HUNKY BEAU SAM ASGHARI SHOWS OFF HIS ROCK-HARD BEACH BOD IN MAUI — PHOTOS

While thousands have likely accosted her at airports, Spears' not above making her own gate side selfie request — even if the Modern Family star she asked for a snap hadn't the foggiest clue who she was. But after the pop star tweeted the pic, O'Neill recounted, "My manager texts me and goes, 'What is this? 53,000 likes. It's Britney Spears.'" Oops! He'll… never do it again?

Though he crawled on all fours while getting smacked with a whip during Spears' bondage-themed performance of her song "Freak Show," Cohen's greatest indignity of the night was likely when the pop star spaced on his name altogether, asking her audience to "give it up for… him!" Him for the win!