With all that onscreen carnage on The Walking Dead, the hit zombie drama is always in need of new blood. The AMC series is beefing up its regular cast ranks with the promotion of Chad Coleman, Sonequa Martin-Green and Emily Kinney for the upcoming fourth season. Coleman plays Tyreese, Martin-Green plays Sasha, and Kinney plays Beth Greene. Kinney has been on the show since 2011, Martin-Green and Coleman since last year. The trio joins another recentWalking Dead regular cast addition, David Morrissey, who has been upped to regular for Season 4.