Williams appeared in "", a show based on a book by "The Wire" creator David Simon, where he guest-starred as Casper in the episode "The Why Chromosome". He had a small guest starring role in "The Sopranos" episode "46 Long" as Special K, an incompetent stickup man and one of Brendan Filone's goons. He went on to play series regular, inmate Kenny Wangler, in the first four seasons of "Oz". He then appeared in HBOs "The Wire" as Bodie Broadus, a Barksdale Organization drug dealer who slowly rises through the ranks throughout the seasons. In preparation for the role, he walked around Baltimore's inner city during the middle of the night a few days before the first taping; talking about this to AllHipHop, Williams stated "it was like 12 or 1:00 in the morning. I just threw on a black hoodie and walked around. I went to one of their hoods and watched that night. I learned not to do that no more, I was lucky I made it back that night." He is older than his character by 8 years.