Simon Cowell Talks 'AGT' Holiday Special & Past Winner Grace VanderWaal

Simon Cowell attends the launch of Britain's Got Talent at BFI Southbank on March 22, 2012 in London, England.

NBC's America's Got Talent is switching gears this season to give viewers a two-hour Holiday Spectacular special, with special performances by Andra Day, Pentatonix, Penn & Teller, along with past season favorites including Grace VanderWaal, Jackie Evancho, and Matt Franco.

"We're singing some Christmas songs," judge Simon Cowell told On Air with Ryan Seacrest over the phone on Thursday. "This could be the greatest Christmas show ever made I think. Heidi [Klum] sings a song, which trust me, you are never going to forget what you're going to see."

Also during the interview, Cowell spoke about VanderWaal, who was dubbed "the next Taylor Swift" by Cowell and judge Howie Mandel after she dropped a memorable performance of her own song "I Don't Know My Name."

"She is like the smartest 12-year-old girl, honest to God. It's like talking to a 50-year-old person. She's brilliant," Cowell said, before touching on her future: "You got to help and turn someone into an artist, and I think that's what she is already. I think she's going to be around for a long time, I really do."

America’s Got Talent Holiday Spectacular is slated to air at 8 p.m. December 19 on NBC.

Original article by Marc Inocencio at iHeartRadio