There are a number of plays called Black Sheep.
Black Sheep (1868) by Edmund Yates (1831–1894) and John Palgrave Simpson
Adapted for the stage from Yates's published novel Black Sheep (Tinsley brothers, 1867) by Yates and Simpson, it was first performed at the Royal Olympic Theatre on 5 April 1868.
Performances in South Africa
Black Sheep by Elmer Rice (1932)
A comedy in three acts that opened at the Morosco Theatre in New York City Oct 13, 1932 and played through Oct 1932, directed and produced by Rice.
Black Sheep by Lee Blessing (2001)
After a public reading at the Arena Stage in Washington D.C. October 19-27, 2001, it formally opened at the Florida Stage in Manalapan, Florida in December 14 of the same year.