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In 22 years of "The Tonight Show," Jay Leno has poked fun at presidents, celebrities, and every day people in the news, but none more than former president Bill Clinton.  George Mason University studied 22-years of jokes and found Bill Clinton was the most joked about person with 4,607 jokes, topping the political targets list. O.J. Simpson was the most targeted celebrity with 795 digs.  Jimmy Fallon is getting ready to take over as host starting February 17th.