President Obama will appear at his fourth White House Correspondents' Dinner on Saturday, the one night a year where the president gets to play stand-up comedian, reading jokes written by professional funny people that poke fun at himself, Congress, and during election years, other presidential candidates. (We're betting it's less than three minutes till the inevitable "Oops!" gag.) This year's event is timed well: President Obama will present to a warmed-up crowd after he slow jammed the news and showed off his self-deprecating sense of humor during an appearance on Late Night With Jimmy Fallon this week. Although this has never really been a tough room. Who doesn't like to see the leader of the free world toss out a zinger or two? But on occasion, past presidents (and Obama) have really made us LOL. Watch our video here for a look back at ten great jokes of past White House Correspondents' Dinners.