until the radiation levels return to normal—a process that takes three million years. Lister therefore emerges as the last human being in the universe—but not alone on board the ship. His former bunkmate and immediate superior Arnold Judas Rimmer (a character plagued by failure) is resurrected by Holly as a hologram to keep Lister sane. They are joined by a creature known only as Cat, the last member of a race of humanoid felines that evolved in the ship's hold from Lister's pregnant cat during the three million years that Lister was in stasis. The series revolves around Lister being the last human alive, after three million years of travel from Earth, with his companions. The crew encounter phenomena such as time distortions, faster-than-light travel, mutant diseases and strange lifeforms (all evolved from Earth, because the series has no aliens) that had developed in the intervening millions of years. Though it has a science fiction setting, much of the humour comes from the interactions of the characters, particularly the laid-back Lister and the stuck-up Rimmer. Despite the pastiche of science fiction used as a backdrop, Red Dwarf is primarily a character-driven comedy, with science fiction elements used as complementary plot devices. Especially in the early episodes, a recurring source of comedy was the Odd Couple-style relationship between the two central characters of the show, who have an intense dislike for each other yet are trapped together deep in space. In Series III, the computer Holly changes from male (Norman Lovett) to female (Hattie Hayridge), and the mechanoid Kryten (who had appeared in one episode in Series II) joins the crew and becomes a regular character. In Series VI, a story arc is introduced where Red Dwarf has been stolen, and the crew pursue it in the smaller Starbug craft, with the side effect that the character Holly disappears. Series VII is also set in Starbug. Early in series VII, Rimmer departs (due to actor Chris Barrie's commitments) and is replaced by Kristine Kochanski, Lister's long-term love interest, from an alternate universe. Kochanski becomes a regular character for Series VII and VIII. At the end of Series VII, we learn that Kryten's service nanobots, which had abandoned him years earlier, were behind the theft of the Red Dwarf at the end of series five. At the beginning of the eighth series, Kryten's nanobots reconstruct the Red Dwarf, which they had broken