because he feels like it. and nbc can't find anyone better.
Yes he was in at least on episode as a biker, trying to get Alice to run away with him.
Jay Leno never had a guest host. He would just air a rerun of a previous show.
Jay Leno (b. April 28, 1950) is a talk show host. Starting in 1992, he was the host of NBC's The Tonight Show With Jay Leno. In 2009, Leno left The Tonight Show to be replaced by Conan O'Brien. He...
Jay Leno hosted The Tonight Show for 17 years.