(Portland, OR) -- Comedian Katt Williams is pleading not guilty to an assault charge after being arrested Saturday in Portland. Williams appeared in a Multnomah County courtroom yesterday on a charge of fourth-degree assault. Williams is accused of attacking a private town car driver Friday after arguing about taking him and his dog to a scheduled performance in town. The driver was treated at a hospital for minor injuries. Police say Williams is also being held on a "fugitive hold" for an active warrant out of Georgia.