Melissa McCarthy "begged" for her role in 'The Little Mermaid'.

The 52-year-old actress plays Ursula the sea witch in Disney's new live action remake of the beloved 1989 animated classic, but she has admitted she wasn't in consideration for the part until she really put herself out there.

She told Collider: "I wasn't up on the list, I wasn't on the list, I wasn't list adjacent, and I was like, 'I'm not gonna get it', but I knew I had to at least make a play for it because I was like, 'I'll be so mad at myself forever if I didn't even try to get, you know, turned down.'

"And I couldn't call Rob because I didn't have (director) Rob Marshall’s number, but I knew a guy who knew a guy, and I just said, 'Can I please come and talk to you? Can I just tell you what Ursula means to me?'

"And then, I never thought I would get it. So, I was not asked, I begged to do it, and I'm so glad I did."

McCarthy is delighted with the finished movie, and insisted even she couldn't see "any of the work" done by the CGI department to bring everything to life.

She said: "The first thing that struck me – first, it’s so beautiful, and I was like, 'We're underwater, I'm not seeing any of the work,' which is, I think, what you can always say when everything's going right.

"You're like, 'I'm not seeing any of the work. I feel the emotion, I feel the story,' which means everybody's doing, like, bionically good work."

The actress also had high praise for Halle Bailey, 23, who plays Ariel, particularly when it came to recreating the iconic 'Part of Your World' routine and taking it beyond singing about wanting "to do different stuff".

She added: "It was about, like, 'I am going to determine my own life,' and there was just moments when Halle's face was so… you felt her heart and her courage, and I thought, 'This is such a different way for so many people to see a Disney Princess'.

"It's with this determination, and like, 'You will not assign me my life,' and I got so choked up, and I was so proud of her. That's a big difference."

"It's not a whole new number, it's not a whole thing, but those little differences that Rob and John [DeLuca] and Disney made, and Halle did, it's all through the movie.

"Those things making it relevant to today meant so much to me, and those were really the moments that just went right to my heart."