Madonna calls Amy Schumer to the stage as Hollywood star becomes the latest celebrity to take part in touring pop legend's raunchy dance interlude

Madonna had a helping hand on Tuesday evening as her Celebration Tour fulfilled the second of two consecutive shows at New York's Madison Square Garden. 

The pop legend, 65, is currently filling stadiums across the world with her mammoth 79 date tour, a retrospective look at her shifting musical styles and numerous image changes over a colourful 40-year career.

Taking to the stage in New York on Tuesday, she was joined by Hollywood actress Amy Schumer while playfully judging her backup dancers on their raunchy choreography skills. 

Fans cheered as both held up placards bearing the number 10, indicating they were pleased with Madonna's stage entourage. 

The singer previously invited actress Julia Garner to the stage for the same judging skit while performing at Brooklyn's Barclay's Center in December. 

Other celebrities to have featured in the judging interlude include Debi Mazar, Donatella Versace, Arca, and Diplo. 

Madonna also sang happy birthday to her 'humble and kind' daughter Chifundo 'Mercy' James Kambewa Ciccone, who turned 18 during her first sold-out Madison Square Garden concert in Manhattan on Monday.

The Queen of Pop also posted a birthday tribute to Mercy, in which she performed composer Erik Satie's 1893 song Gnossienne No.1 on piano.

'Beautiful Chfifundo James you're 18 [years] old today!' Michigan-born Madge - who boasts 52.2M social media followers - wrote on Instagram.

'Beautiful Mercy James you're already a young woman! Beautiful African queen! You surprised all of us! You were always the quiet one. The gentle one. The shy and stoic one. 

'While all of my other children were clamoring for attention, you were hiding under your hoodie — never wanting to draw attention to yourself.

'Always humble and kind. Always the first one to say thank you [and] to clear the table after dinner! To come and hug me and say how much you appreciate something.

And always the most [responsible]. Beautiful Mercy James I am really astounded by the woman you have become. Poised and radiant. Skilled and soulful. A true artist.' 

While on tour, the seven time Grammy winner enlists Mercy to accompany her on piano for her 1992 track Bad Girl as well as a bit of Chopin.

'That hand that was once frozen in your mouth as a child now makes magic happen when you play the piano,' Madonna wrote.

'Whether its Erik Satie or Chilly Gonzales. To hear you play Chopin every night in my show with such confidence is such a thrill.'

Madonna has teamed up with creative director Lewis James and musical director Stuart Price to dream up her most spectacular stage presentation for her 12th concert tour honoring her four-decade career.

Rather than a band or singer, the Popular singer enlisted RuPaul's Drag Race #8 champ Bob the Drag Queen to serve opening act duties for her.

The singer also plans to  embark on her self-directed Universal Pictures biopic - titled Little Sparrow - starring three-time Emmy winner Garner.

The Evita alum co-wrote the script with Oscar-winning screenwriter Diablo Cody, who was later replaced by Independent Spirit Award-winning screenwriter Erin Wilson.