The murder mystery, a work of historical fiction, will debut on The Network next year.
Mulaney, who will soon star in All In: Comedy About Love on Broadway, served as host for the October 2 airing.
The episode will be something of a Spring Awakening reunion, reconnecting Groff with Gideon Glick.
The NBC broadcast will also feature the Radio City Rockettes, Lea Salonga, Idina Menzel, and Ariana Madix.
Your guide to where and when to watch captures of live plays and musicals.
Aleshea Harris's play premiered Off-Broadway in 2018 at Soho Rep.
Ozian witches past and present gathered to celebrate the release of the film adaptation of the Broadway musical.
Get a first listen to Cynthia Erivo's "I'm Not That Girl," Ariana Grande's soprano, and more.
Pasek and Paul will also produce the movie adaptation, which is in development at Apple.