Johnny Carson plays an elaborate practical joke on Joan Rivers (about 1983). Because of her many jokes about the British Royal Family, Johnny Carson hires British actress Janet Brown - notable for playing Prime Minister Margaret Thatcher - to fool Joan Rivers into thinking she is the Prime Minister, who confronts and scolds Joan Rivers about her material.
Rivers' late husband Edgar Rosenberg is briefly seen in this video. In her panic while being confronted by "Margaret Thatcher", Rivers says: "Edgar, why don't you sit here?"
Due to the falling out between Joan Rivers and Johnny Carson after she left her position as permanent guest hostess on his show to host her own competing talk show on Fox, this has not been broadcast since 1985.