Taylor Momsen didn't know what Jim Carrey looked like while filming How the Grinch Stole Christmas

Taylor Momsen didn't know what Jim Carrey looked like until she met him at the premiere of their 2000 movie How the Grinch Stole Christmas.

The actress-turned-rock star, who was only five years old when she was cast as Cindy Lou Who, has admitted that she never saw the comedy legend without his costume and prosthetics on set so she didn't know what he actually looked like until the premiere.

"The funny thing is I never knew what Jim Carrey looked like because I never saw him because he was there (on set) way early doing the prosthetics," she shared on the Call Her Daddy podcast. "I didn't know who Jim was until the premiere and someone had to point him out to me and go, 'That's Jim.' And I went, 'Oh, Jim.'"

Carrey spent many hours in the hair and make-up trailer transforming into Dr. Seuss's grouchy green character. Although she was young at the time, Momsen, now 32, remembered being under so many layers of prosthetics "killed" her co-star.

"It killed him, from what I remember, it was brutal," she said. "If I remember correctly, I think he went through actual torture training with a Navy SEAL guy to learn how to deal with it because he is so covered."

While some young viewers were scared of The Grinch, the former Gossip Girl star insisted he was "never scary" to her, even as a child.

"To me, he was always Jim and he was always in make-up. He was very protective of me, very kind, super funny, super animated, absolutely awesome," she praised.

This year, Momsen has recorded a rock version of Where Are You Christmas?, the song Cindy Lou Who sings in the movie, for her band's festive EP, Taylor Momsen's Pretty Reckless Christmas.