The characters were singing “People Let me Tell you about my Best Friend” when the song suddenly stopped and the intro to “Never Gonna Give You Up” began to play. The door on the float opened and NONE OTHER THAN THE RICK ASTLEY came out and started singing the song!!!! At the end the character named Cheese turns to the camera and shouts, “I LIKE RICKROLLING!!”
Seriously, it was the most BRILLIANT thing ever! Made my Thanksgiving!
UPDATE: Ghetto video version:
More over at Cnet.