Mariah Carey found her appearance in Precious: Based On The Novel Push By Sapphire a real "fright".
The pop diva had to forego her make-up to play dowdy social worker Mrs Weiss in the movie, which has won rave reviews.
"It was a fright! The overhead lighting was not my friend and I hated the way my hair looked," she admitted.
Mariah was so unhappy with her on-screen appearance, she even tried to sneak on blusher when director Lee Daniels wasn't looking.
"I was just trying to give it a little something. One of my make-up artists said, 'This is a Mariah Carey nightmare, everything that you hate is going on right now'," she explained.
"But it was cool because a lot of people tell me they don't recognise me in the film, they don't know it's me, and to me, that was a great gift that Lee gave me to be able to go that far away from who I am."
Lee, who initially approached Dame Helen Mirren for the part, was thrilled with Mariah's transformation.
"I said, 'Mariah, you've got to come solo. You can't come with your posse, you can't come with a scrubbed face, there's no make-up. We've got to make you more ugly!'" he said. "I knew she could do it, but I didn't think she would go to where she went. I'm so happy because her performance is so unexpected."
:: Precious: Based On The Novel Push By Sapphire is in cinemas now.