Dr. Leo Dreyfus, portrayed by Christopher Lloyd, is a CIA psychiatrist assigned by General Beckman to treat Chuck when the malfunctioning Intersect appears to be giving Chuck nightmares and threatening his sanity.
Upon initially meeting with Chuck, Dreyfus orders that he is to be removed from field duty and later has him institutionalized after an apparent unprovoked attack on a visiting dignitary and scientist Dr. Kowambe, under the impression from the Intersect that there is an intelligence hidden in one of his teeth. Later, at Sarah's insistence, Dreyfus allows her and Casey to visit him after hours in an effort to help Chuck through his apparent mental impairment, and fortuitously they arrive in time to rescue Chuck from Kowambe, who reveals he works for the Ring and attempts to kill Chuck for his knowledge on the Ring's intelligence hidden in one of his teeth. In light of the realization that the Intersect's interactions with Chuck's dreams proved correct, Dreyfus cleared Chuck for return to duty. He is fully aware of Chuck's identity as the Intersect, and is concerned that the computer may eventually overwhelm Chuck's mental faculties entirely in the near future.
Seen in: "Chuck Versus the Tooth".