For the 15-year anniversary concert, A Very Wicked Halloween, Adam Lambert, Ariana Grande, Ledisi, Pentatonix and other artists will be singing iconic songs from the hit 2003 Broadway musical Wicked with the original Elphaba, Idina Mendel and Glinda, Kristin Chenoweth.
American Idol contestant and Grammy nominee Lambert eventually played love interest Fiyero during the 2005 national tour.
He said, "Word on the street was there's this musical, and it's amazing."
Lambert will be singing "As Long As You're Mine" with Ledisi, who has also worked in theatre in productions of Caroline, or Change and The Color Purple.
Pentatonix member Kristin Maldonado told Playbill, "The second the soundtrack came out I feel like everyone was obsessed with it."
Fellow Pentatonix member Mitch Grassi noted, "It's a full circle moment, we grew up with this show and the [album] kind of shaped us as performers."
Wicked, which was adapted from the book of the same name by Gregory Maguire, tells the story of the misunderstood Wicked Witch of the West from L. Frank Baum's classic books and the 1939 film The Wizard of Oz.
A Very Wicked Halloween will be showing on NBC on October 29, 2018.