The 42-year-old theater star visited the late-night show in New York City directly after arriving home from her trip to L.A. for the Oscars, where she performed the song for the first time ever on live TV.
Fallon sat beside Menzel, tapping a trio of alphabet blocks. The Roots backed the stars up with a variety of instruments, including the xylophone, kazoo, tambourine, ukulele and keyboard harmonica.
During his opening monologue, Fallon poked fun at John Travolta butchering Menzel's name at the Academy Awards. "He could tell as he was saying it, 'This is not going to come out right at all—I'm gonna say sounds,'" he joked. "When Idina Menzel heard that, she was like, 'Let it go. Let it go. Let it go.'"
Travolta accidentally called Menzel "Adele Dazeem" when he introduced her performance Sunday; a source later told E! News that the actor pronounced her name correctly during rehearsals: "He knew how to say her name. No one knows what happened. Maybe nerves just got the best of him."
Menzel's attention is now on her Broadway musical, If/Then, which begins performances this week.