Jennifer Lawrence and Amy Schumer danced on Billy Joel's piano at his Chicago concert on Thursday (27.08.15).

The celebrity pals - who are currently writing a screenplay together - appeared on stage during his performance of 'Uptown Girl', where they shimmied around to the song, which features in Amy's movie 'Trainwreck.'

At one stage Jennifer was even seen kissing Amy's bare feet as the comedian climbed on to the piano.

Earlier in the day, the pair rehearsed with Billy at Wrigley Field before the show.

Amy and Jennifer have become firm friends ever since the 'Hunger Games' star reached out to the 34-year-old actress after seeing her comedy 'Trainwreck'.

Asked how they became friends, the 25-year-old Oscar winner said: ''I emailed her after I saw 'Trainwreck' and said, 'I don't know where to get started. I guess I should just say it: I'm in love with you.' We started emailing, and then emailing turned to texting. We really hit it off, to say the least.''

The duo are now working on a screenplay and plan to co-star in the upcoming movie together.

Jennifer told the New York Times: ''We play sisters. We're almost done writing. It just flowed out of us. We've got about 100 pages right now.

''Amy and I were creatively made for each other. It's been the most fun experience of my life. We start the day off on the phone, laughing. And then we send each other pages. And we crack up.''