Billie Eilish surprises Alicia Keys with throwback Fallin' performance on The Late Late Show

Billie Eilish continues to clock up celebrity fans, from the surprising (Dave Grohl) to the adorable (Harper Beckham, who dressed up as her for Halloween).

But one recent mega fan emerged on The Late Late Show - Alicia Keys, who has covered her hit single 'Ocean Eyes' previously.

Keys was filling in for James Corden and shared her love of the teen popstar with her. "I'm a super, super fan of yours... I love your music, I love your voice, I love your style, I love your energy, I love who you are as a human," Keys raved to her in a video that already has more than two million views.

Keys is such a fan that she previously covered Eilish's song 'Ocean Eyes' on her Instagram.

In return, the 17-year-old indie popstar played a video of her covering 'Free Fallin' at a talent show five years ago.

In the throwback video, Eilish hasn't exactly embraced her signature style yet - instead, she appears to be wearing an Old Navy American flag tee, which she would only wear ironically onstage these days.

Eilish has six Grammy nominations, including Album of the Year - and Keys just so happens to be hosting this year.

Perhaps they'll collaborate - Eilish and Keys played a version of 'Ocean Eyes' on The Late Late Show, complete with Keys accompanying the teen star on piano.