John Oliver returned to his old stomping grounds with a surprise cameo on "The Daily Show" to discuss America's "monarchy era."

John Oliver reunites with Jon Stewart on The Daily Show after 10 yearsSource: The Daily Show The president lashed out at the pop star on his social media website. The NFL said the person was part of the 400-member field cast and had hidden the flag on himself before the halftime show began Sunday night.

On Monday, perhaps the most successful alum of the Jon Stewart-era of "The Daily Show" is John Oliver, host of "Last Week Tonight," made a surprise return to the show. But he wasn't there just to bro-out with Jon Stewart.