Yes he was a guest.
No, he was a guest on Jay Leno's show on October 24, 2012.
terry bradshaw (50)
As a publicity stunt, Katie Couric is the only person to guest host Jay Leno's Tonight Show when she & he switched jobs for a day. He guest anchored TODAY on May 12, 2003.
Jay Leno never had 1 guest host in the history of his show, Katie Couric. She did it for one show. Other than that, usually, he would just air a rerun of a previous show.
Jay Leno is the host of NBC's "The Tonight Show with Jay Leno". He was also the host of "The Jay Leno Show".
Jay Leno was Johnny Carson's permanent guest host before he became its host after Johnny Carson retired.