Nichelle Nichols played Nyota Uhura on Star Trek. She didn't like television work and wanted to get back to the theater. So she told the producer, Gene Roddenberry, that she planned to leave the show after the first season. He begged her to take the weekend to reconsider.
She agreed. Later, Nichols attended a fundraiser. Martin Luther King, Jr. was there. He approached her and expressed that he was a huge fan of her work. When she informed him that he planned to leave the show, King implored Nichols to stay. Lt. Uhura, King argued, wasn't a servant or some other black stereotype, but a professional and a leader.
Watch the above video as Nichols tells the story of how Martin Luther King, Jr. persuaded Uhura to remain on the Enterprise.
-via The Geek Twins