FBI Special Agent Fox William Mulder () is a fictional character in the Fox science fiction-supernatural television series "The X-Files", played by David Duchovny. Mulder's peers consider his (often correct) theories on extraterrestrial activity as spooky and far-fetched. With his FBI partner Dana Scully, he works in the X-Files office, which is concerned with cases with particularly mysterious or possibly paranormal circumstances that were left unsolved and shelved by the FBI. Mulder was a main character for the first seven seasons, but was limited to a recurring character for the following two seasons. He returns as a main character for the tenth and eleventh seasons.