Doctor Who celebrated its 20th anniversary with the 90-minute special "The Five Doctors." The life of the present Doctor (Peter Davison) is jeopardized when his four previous incarnations -- played by William Hartnell, Patrick Troughton, Jon Pertwee, and Tom Baker -- are taken out of time by an illegal Time Scoop. Even worse, the five doctors are confronted by a seemingly endless series of past enemies, included Daleks, Cybermen, and Yetis. The climax takes place in the Forbidden Zone on Gallifrey, where the instigator of the aforementioned time-scooping forces the five doctors to engage in the potentially deadly Game of Rassilon. Can any of the doctors save themselves -- and if not, will robot dog K-9 come galloping to the rescue? The late William Hartnell appeared only in clips from the second-season episode "Invasion of Earth: Flashpoint"; he was replaced in the body of the 20th anniversary special by Richard Hurndall. Written by Terrance Dicks, "The Five Doctors" was first presented in America on November 23, 1983, two days before its British TV debut. Since that time, it has been reedited into a four-part cliffhanger for syndication.