A frustrated Clarkson begged the band to play a song she knows, but when they started playing her hit, "Since U Been Gone," it was Hathaway who stepped up to the mic first. The epic moment sent Clarkson to the floor as Hathaway continued to belt out the early aughts tune.
The WeCrashed actress rubbed the win in the talk show host's face, walking over to a flabbergasted Clarkson to literally drop her mic.
"How did you know it from just that?!" an astonished Clarkson asked.
"Kelly Clarkson, if you do not understand how much we all love that song. Everybody here knew it on the first one," Hathaway said. "Everybody here knew it."
"Should I just quit?" Clarkson joked.
"I love that song," Hathaway maintained, taking a four to nothing lead.
"This is embarrassing," Clarkson continued.
ET spoke with the multi-talented actress at the premiere of her new Apple TV+ series, where she gushed over her special connection with her co-star, Jared Leto.
"He's so sweet. He's really playful and we just make each other laugh. We have a really gentle thing," Hathaway told ET. "The little that I know about Jared, is that he cares about what he does, body and soul, so much. And I'm the same way. So, to be able to connect like that over a shared passion, something that we both really love giving ourselves fully to -- in a way that I get it, it's unusual -- it was really, really special. I feel really lucky that he was my partner in this."
Leto wasn't the only one to commit to his character. Hathaway started a whole new diet to play the role of Rebekah Neumann, the wife of WeWork CEO, Adam Neumann (Leto), in the series, which not only tells the story of the company's rise and fall, but the love story at the center of one of the world's most valuable startups.
"I didn't commit to it. I just found myself there in the end," Hathaway said of her raw vegan diet. "She kinda took hold."
It's not all bad though, with Hathaway joking, "I love it -- until I don't."
It's unclear if Hathaway is still on that raw vegan diet after the cupcake hack she showed Clarkson on Tuesday. Check out the video below to see the genius way Hathaway eats the sweet treat.