The story:

In 2006, he gained notoriety for an incident in Philadelphia as a part of Opie and Anthony's Traveling Virus Comedy Tour. After the crowd began to boo him mercilessly, Burr decided to fight back. He abandoned his scripted material entirely, proceeding to hurl profanity-laced insult after insult toward the crowd themselves and the city of Philadelphia. He continued in this off-the-cuff manner for over ten minutes, and was treated to a lengthy standing ovation as he left the stage.