Jay Leno's top joke targets were Bill Clinton and O.J. Simpson

Jay Leno steps down from his role as host of "The Tonight Show" on Thursday, a position he has held almost continuously since 1992. He has more than 4,600 shows under his belt -- that's a lot of monologue jokes. Bill Clinton was one of the biggest target of those jokes. As far as politicians go, anyway. For celebrities, it was O.J. Simpson.