Martin Sheen, Tricia Helfer sounding off in Mass Effect 2

BioWare secured a handful of big names to lend celebrity gravitas to the original Mass Effect, tapping the likes of Modern Warfare 2's Keith David and Lance Henriksen for voice-over work. With Mass Effect 2 slated to arrive for the Xbox 360 and PC on January 26, BioWare today announced both David and Seth Green will reprise their respective roles as Admiral David Anderson and Normandy pilot Joker.

Martin Sheen (Apocalypse Now, The West Wing) is perhaps the most celebrated new addition to Mass Effect 2's voice cast. The Emmy and Golden Globe Award-winning actor will portray the enigmatic "Illusive Man," commander of a humancentric secret society called Cerberus. Fellow Emmy Award winner Shohreh Aghdashloo (House of Saddam, The Sisterhood of the Traveling Pants 2) will also lend her voice to the sci-fi role-playing game as Admiral Shala'Raan vas Tonbay.

Chuck's Adam Baldwin and Yvonne Strahovski will voice the characters of Kal ‘Reegar and Miranda Lawson, a Cerberus operative. Michael Dorn, of Star Trek: The Next Generation fame, will lend his baritone to Gatatog Uvenk, while Carrie-Anne Moss (The Matrix, The Matrix Revolutions) will portray planet Omega crime lord Aria T’Loak.

Tricia Helfer, who just recently lent her voice to Bungie's Halo 3: ODST and will also portray Kerrigan in Starcraft II is onboard as EDI, better known as the new voice of the Normandy. Helfer's Battlestar Galactica costar Michael Hogan (aka Saul Tigh) will assume the role of Captain Bailey.

Mass Effect 2 begins with the original game's hero, Commander Shepard, embarking on a dangerous mission to the mercenary-controlled Omega mining facility. While BioWare has remained tight-lipped on further plot details, the sequel will provide continuity by importing character decisions made in the original game. Check out BioWare's just-released trailer, below, to hear the newly announced voice cast in action.