Martin Platt will stage the reading of the play at the Lucille Lortel Theatre, which centers on "Lily, a fabulous dramatic diva who must fend off a challenge from her ambitious but naïve understudy."

In addition to the previously announced Johnston, Sheffield Chastain, Catherine Curtin, Roderick Hill, Jeremy Lawrence, Mark Pinter, Allen Lewis Rickman and Jeff Steitzer, the 7:30 PM reading will also feature Amy Fitts, Shannon Koob, Paul O’Brien, Allen Lewis Rickman, Gareth Saxe, Kraig Swartz, Peter Van Wagner, John C. Vennema, and Margot White.

Watkins is the late playwright of Chicago (the basis for the Kander and Ebb musical), as well as the screenplays "Libeled Lady" and "Roxie Hart."

Kristen Johnston appeared in the world premiere of Theresa Rebeck's The Understudy at the Williamstown Theatre Festival last summer. Best known for her television work on "3rd Rock from the Sun," Johnston has appeared on Broadway in the revival of The Women and is a frequent guest of Celebrity Autobiography.

For tickets, priced $40-$250, phone (212) 315-0231 or visit MintTheater. The Lucille Lortel Theatre is located at 121 Christopher Street in Manhattan.