In 1967, Martin Luther King, Jr urged Nichelle Nichols to stay in her post as Lt. Uhura on Star Trek because she was an important and all-too-rare positive TV role model for black people. From CNN:
As the startlingly beautiful and fiercely intelligent Lt. Uhura on the hit 1960s TV series, Nichols was a revolutionary figure at a time when the only African-American women you saw on U.S. TV were usually playing servants.
Indeed, Star Trek was reportedly the only program Martin Luther King Jr would let his children stay up late to watch.
When Nichols was considering leaving the show to pursue a career on Broadway, King Jr personally implored her to stay, saying she was a powerful role model for black people across the country -- and the world. "That was the greatest thing," says Nichols. "That was greater than anything else, to be told that by Dr. Martin Lurther King, because he was my leader.
"So I stayed and I never regretted it."