"I was super nervous. The day didn't start off so well," she admitted. "I was singing, there was snow falling, I looked up, trying to make it magical and beautiful, and ended up choking on the snow and vomiting on the ground. And they have it in slow-mo, on film."
Kimmel was quick to point out how great it would be to see that on the DVD extras.
"At first I was sort of worried, because Idina sang it and Demi [Lovato] sang it...you know, so many people have done it. But I got Idina's blessing, which was wonderful," she revealed. "We were sort of tweeting each other, and she knew it was happening."
Following her embarrassing moment, the 28-year-old got another surprise when some of the crew members brought their kids to set and thought Lea was the real-life Elsa. "I realized, I turned to their parents, and I was like, 'Oh, they think I'm her,'" she recalled. "And then it was awesome. I was like, 'I am god right now. I am a Disney princess god!'"
Who do you think sang "Let It Go" the best: Lea, Idina or Demi?