That time that Martin Luther King Jr. ad-libbed the 'I have a dream' speech

August 28th marks the 50th anniversary of the historic civil rights march in Washington D.C. that culminated with Dr. Martin Luther King Jr.'s infamous "I have a dream speech." In an effort to celebrate the historic occasion, PBS plans to air a documentary called The March on the eve of the anniversary. Denzel Washington is set to narrate the piece.

Among the tidbits to come out of a recent press event promoting the special is the fact that Dr. King ad-libbed the most memorable portions of the speech. Clarence Jones, one of Dr. King's advisors who had helped on an early draft of the speech, says that gospel singer Mahalia Jackson spoke out to King as he addressed the crowd from the steps of the Lincoln Memorial, forever altering the course of history.

"When Mahalia shouted to him, I was standing about 50 feet behind him... and I saw it happening in real time. He just took the text of his speech and moved it to the left side of the lectern. ... And I said to somebody standing next to me: 'These people don't know it, but they're about to go to church.' I said that because I could see his body language change from the rear. Where he had been reading, like giving a lecture, but then going into his Baptist preacher mode.

"Had there been anyone else -- anyone else -- who had shouted anything to him -- I think he would have been a little taken aback. I'm not so sure he would have departed from the text of his speech. But Mahalia Jackson was his favorite gospel singer. When Mahalia said that it was almost like a mandate to respond." [The Wrap]