Fox website TheSimpsons.com. Retrieved on October 25, 2010 Treehouse of Horror I, II, III, IV, V, VI, VII, VIII, IX, X, XI, XII, XIII, XIV, XV, XVI, XVII, XVIII, XIX, XX Episode guide from Warren Martyn and Adrian Wood's book "I Can't Believe It's a Bigger and Better Updated Unofficial Simpsons Guide" on the BBC website. November 10, 2007 Treehouse of Horror I, II, III, IV, V, VI, VII, VIII, IX Treehouse Of Horror Treehouse Of Horror List