Katy Perry has joked that she's keen to babysit seven-year-old piano prodigy and viral sensation Avett Maness, after the youngster asked for her number.

The online superstar, who is blind and learned to play the instrument by ear, appeared on Sunday's (28Apr19) Queen-themed episode of American Idol and performed a rousing rendition of the band's iconic hit Bohemian Rhapsody.

Speaking to reporters from Entertainment Tonight (ET) after the show, Katy gushed over the Ohio-born star's talent, and confessed that he's also a fan of her's.

"He asked me for my number backstage," the Swish Swish star laughed. "I was like, 'You're seven!' I mean, I'm down to babysit."

The 34-year-old went on to boast about her babysitting abilities, and joked that fiance Orlando Bloom would have nothing to worry about as the pair would spend their time eating cookies.

"I'm a great babysitter - I let the kids eat all the Oreos," the songstress quipped.

Katy's co-judges Luke Bryan and Lionel Richie were also impressed by the young performer's bold move, with the country star joking that the youngster was "getting the digits" and the Hello hitmaker laughing that he'll be a "killer" by the age of 19.

Last week, the hit Fox show celebrated Disney's extensive songbook, and the Firework hitmaker turned up to judge the singing competition dressed up as The Little Mermaid's villain Ursula, complete with moveable tentacles and a purple bodysuit.

Speaking to ET after the episode, the I Kissed A Girl star explained her thought process behind the unusual ensemble.

"I was thinking about (being) the Little Mermaid (Ariel) but then I realised, Ursula is a character who isn't done very much, (while) the Little Mermaid always gets her moment in the sun!" she shared. "And Ursula, actually, really wants Ariel's voice. And that's what I want, is these contestants' voices!"