WATCH: Bernie Sanders brings down the house with hilarious surprise Colbert appearance
Sen. Bernie Sanders with Stephen Colbert on The Late Show - (CBS screen grab)

Democratic presidential contender Bernie Sanders brought down the house on the The Late Show Thursday night, showing up as the "mystery guest" to help host Stephen Colbert pull the lever and  spin the "Wheel of News" -- and ended up mockingly berating the host for how he treats his employees.

After briefly sitting down -- following thunderous applause after being introduced -- to answer a few questions about the campaign and his drive to round-up superdelegates, Sanders demanded an opportunity to pull the lever to "spin that damn wheel."

"Hey! There is a human being down here,"  Sanders exclaimed as found Late Show staffer Brendan holding up the lever while crouched behind the desk. "What is going on. What are you doing to this worker? What kind of operation are you running, Stephen?"

"It's a talk show, Bernie," Colbert smirked

Pulling the lever, the wheel landed on "t-shirt cannon," and the audience went even crazier as the Vermont senator fired t-shirts to the crowd in the upper deck of the theater.

Watch the video below via CBS: