A musical number, a song or a dance or both, that creates such excitement in an audience that the show has to pause because people keep cheering and applauding. Famous showstoppers include Gwen Verdon's apache dance in Can-Can, "Get Me to the Church On Time" from My Fair Lady, and "Sit Down, You're Rockin' the Boat" from Guys and Dolls. And "Mirror Mirror," which I saw in Follies in 2001, brought down the house.