There are a number of plays called Black Sheep.
Black Sheep by Edmund Yates (185*)
is both a children's novel and a play
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.