On the Billboard Pop Shop Podcast, Katie & Keith are also chatting about new Christmas songs from Jimmy Fallon & Meghan Trainor and Jason & Travis Kelce.
The trio performed "Oh Santa!" for the first time at Madison Square Garden Dec. 9.
The song originally came out in 2014.
The trio recorded the track for C
The joyous clip features footage of Lambs rocking out at Mariah's tour stops in their holiday finest.
Lee scored the No. 1 spot after peaking at No. 2 the last four holiday seasons behind "All I Want for Christmas Is You."
The "Heart Attack" singer recounts her favorite moments of making A Very Demi Holiday.
On the new Billboard Pop Shop Podcast, Katie & Keith are talking about Lee's unexpected "Rockin'" rocket ride to the top of the Hot 100 for the first time.
"They wake up in the mornin'/ Thinkin' bout me, Morgan Wallen," the model raps on her new song.
From Carla Morrison's "Noche de Paz" to Charlie Zaa's' "No Me Puede Faltar (Navidad)" and more.