Back in 2011, Donald Trump went on several TV shows to publicly question Barack Obama's US citizenship and suggest his presidency might be one of the "great scams" in history. President Obama responded by inviting him to the White House Correspondents' Dinner, where he proceeded to mercilessly mock the real estate mogul. He called him out as a conspiracy theorist, belittled his reality TV shows, jeered his "credentials and breadth of experience", and jokingly suggested what a White House might look like under a Trump presidency. The public humiliation, in front of his peers and the nation, may well have motivated Trump to run for president. As president-elect, he's certainly had the last laugh. President Obama may regret goading a man who's gone from being a punchline to almost certainly the next president.