Lloyd, whose casting was first announced by the show's co-creator Josh Schwartz via Twitter, will play a therapist who lends Chuck his couch when the pressures of being a spy become too much for him. He will appear in the 16th episode of the season, which will air in April or May.
Lloyd is best known for playing eccentric, time-travelling scientist Dr. Emmett Brown in the Back to the Future trilogy. Schwartz noted in his tweet that the films are a "huge Chuck influence."
Chuck airs its final episode before the 2010 Winter Olympics Monday at 8/7c on NBC.