The 43-year-old actor, whose recent films include Syriana, The Darwin Awards and Fido, joins the existing cast of Edward Norton (playing Hulk/Bruce Banner), Liv Tyler (Betty Ross), Tim Roth (Emil Blonsky) and William Hurt (Gen. Thaddeus 'Thunderbolt' Ross).
Nelson plays an evil scientist called Samuel Sterns, aka The Leader. One of the Hulk's enemies, Sterns is a menial worker in a chemical research plant who is bombarded with gamma radiation. He emerges from his accident not only green-skinned but also super intelligent, with an oversized brain.
Helmed by Transporter director Louis Leterrier, The Incredible Hulk is currently filming in Toronto and Vancouver, Canada. It's due to hit cinemas June 20 2008.