David Zayas, who plays Detective Sgt. Angel Batista, actually was a police officer with the New York City Police Department prior to becoming an actor. Before that he served in the U.S. Air Force.
During Season 8, Angel Batista wasn't always played by David Zayas. His son David Zayas Jr. stands in for his father in some shots, as the two look remarkably alike.
Though they play brother and sister in the series, having met on the show, Michael C. Hall and Jennifer Carpenter married on 31st December 2008. They subsequently divorced in December 2010, but continued to work together in the show.
Series star Michael C. Hall revealed he was afflicted with Hodgkin's lymphoma in January 2010, but continued to work on the series. Most of his fellow cast members were surprised by the news, because he had not disclosed his condition during production. Hall is, as of mid-2010, in remission.
During the first 5 episodes of season 5 Michael C. Hall wore a wig for his role as Dexter due to losing his hair while going through chemotherapy.