"The ultimate #tbt [Throwback Thursday]," Simpson tweeted May 30 along with a YouTube video of her performance of "The Music and the Mirror."
Donna McKechnie originated the role of Cassie in the 1975 musical, earning a Tony Award for her performance. A Chorus Line was revived on Broadway in 2006 with Charlotte d'Amboise as Cassie; she received a Tony nomination for her performance.
Watch Simpson's full performance below: