For stand-up comedians, pulling off a successful stint at the White House Correspondents' Dinner is an uphill battle. Your audience is famously stiff and they also happen to be some of the most powerful people in the world. As Brian Williams once told SNL's Seth Myers "[It's the] toughest room in the business – no man comes out unscathed. Even the knees of brave Achilles would go to jelly were he to stand behind that podium." And the same goes for presidents, who have to juggle the right balance between material that's sufficiently humorous and reasonably presidential. As such, jokes get scrapped and left on the cutting room floor all the time. 

Often times, you never hear about what gets cut. But today, Mark Katz who used to pen jokes for President Bill Clinton, recalled a rather edgy quip from way back in 1998 that was never used.“It was, ‘Looking back, maybe I should have raised money in the Oval Office and had sex in the Lincoln Bedroom,’” Katz told The Washington Times. “I knew that was going nowhere. At the White House, people are very blunt about what lines you cannot cross." At the time, the Monica Lewinksy sex scandal was still fresh in the public's memory and you can imagine how the press might react. Still, Katz has some regrets the joke was never used. "My instincts are to address those topics," he said.

Other times, a joke gets cut for more secretive reasons. Last year, for instance, the raid on Osama bin Laden's compound was being carried out over WHCD weekend. One of President Obama's quips that time around was about Tim Pawlenty's secret middle name: "Hosni" (i.e. Tim "Hosni Mubarak" Pawlenty"). But that wasn't how the president's speechwriter's originally conceived it. At Aspen Idea's Festival, Obama adviser David Axelrod explains how it went down:

As it turns out, Obama's speech writers originally wanted Pawlenty's middle name to be "Bin Laden." But the president nixed the joke, a decision that puzzled everyone, including his former advisor David Axelrod -- until the news broke the next evening.

Axelrod elaborates:

And then you have the comedians. Most comedians say the Correspondents Association gives them free reign to joke about what they want to. However, that doesn't mean that self-censorship isn't happening. Stephen Colbert, who will probably go down as delivering the best stand-up the Association has ever seen, even pulled a few punches. Back in 2009, he told a gathering of Second City alums what he had to pull back and The Atlantic's James Warren was there to catch it:

Colbert disclosed that he did substantial self-editing upon looking at the president and discerning that he wasn't ecstatic. He had planned to play off Medal of Freedom awards Bush had given former CIA Director George ("It's a slam dunk") Tenet and former Iraq administrator L. Paul Bremer; joshing about how Bush was clearly giving awards to everybody in sight.

"'But nobody gives this man an award,'" Colbert recalled as the thrust of the riff he scrapped. "'That ends tonight. I'm going to give the highest honor I can give....a certificate of presidency.'" 

It would be akin to "something you get from The Learning Annex for taking a course. 'I, Stephen Colbert, acknowledge...'" Colbert looked at Bush and said to himself, "I'm going nowhere near this."

So what do we have in store for us this Saturday? With Jimmy Kimmel hosting, no one's expecting an outrageously profane performance. (After all, he's peddled most of his comedy on the safe confines of network television.) Still, you never know if he'll try and surprise this year. The closest thing he gave as a clue was in interviews with Reuters' Mary Milliken and Politico's Patrick Gavin. "I will feast on stupid comments," Kimmel told Milliken. Meanwhile, he told Gavin he may go after Rick Santorum's stance on pornography (rather safe material, we'd say). Hopefully, he at least shocks the stuffy DC audience once or twice. Here's his interview with Gavin: