series IX, "Back to Earth" was partially inspired by Blade Runner (1982). The series' themes are not limited to films or television, having also incorporated historical events and figures. Religion also plays a part in the series, as a significant factor in the ultimate fate of the Cat race, and the perception of Lister as their 'God', both in the episode "Waiting for God" (whose title makes a literary reference to the Samuel Beckett play Waiting for Godot), as well as the crew meeting a man whom they believe to be Jesus Christ in series X episode "Lemons". The series VII episode "Ouroboros" derives its name and theme from the ancient mythological snake of the same name. The third episode of series VI, "Gunmen of the Apocalypse", was based on the Four Horsemen of the Apocalypse. The series explores many science-fiction staples such as time-travel paradoxes (including the grandfather paradox), the question of determinism and free will (in several episodes), the pursuit of happiness in virtual reality and, crucially to the show's premise of Lister being the last human, the near-certainty of the human species' extinction some time in the far future. Aliens do not feature in the series, as Grant and Naylor decided very early in the process that they did not want aliens involved. This is usually addressed with Rimmer's belief in extraterrestrial life being shot down, such as a vessel he believes to be an alien ship turning out to be a garbage pod. However, there are non-human life forms such as evolutions of Earth species (e.g. the Cat race), robotic or holo-life forms created by humans, and a kind of "genetically engineered life form" (GELF), an artificially created creature. Simulants and GELFs frequently serve as antagonists during the later series of the show. Hallmarks The series developed its own distinct vocabulary. Words and phrases such as hologrammatic, dollarpound, bazookoids, Felis sapiens, Simulants, GELF, space weevil, and Zero Gee Football appear throughout the series, highlighting a development in language, political climate, technology, evolution and culture in the future. The creators also employed a vocabulary of fictional expletives to avoid using potentially offensive words in the show and to give nuance to futuristic colloquial language; in particular, "smeg" (and variants such as "smegging", "smegger", and "smeg-head") features prominently, alongside the terms "gimboid", "goit" and "Gwenlan". Episodes Ratings Red Dwarf I Red Dwarf VIII Back to Earth Red Dwarf