Nothing was off limits Saturday night at the annual White House Correspondents' Dinner — not even dogs. Obama humored the crowd of celebrities and Washington elite with quips about recent canine campaign drama.

"Of course, I know everybody is predicting a nasty election," he began. "And thankfully, we've all agreed that families are off limits. Dogs, however, are apparently fair game."

The president showed an ad from a fictional PAC called WOOFPAC, which declared that America's dogs can't afford four more years (or 28 more dog years) of his presidency. The clip poked fun at rival Mitt Romney's much-publicized error of strapping his dog's crate to his car roof during a road trip to Canada in the 1980s.

"My stepfather always told me," he said in a moment of self-deprecating humor, "It's a boy-eat-dog world out there."