Sci-fi staples are a common theme in science fiction, and include spaceships (10 letters), ALIENS (6 letters), ETS (3 letters), UFOs (4 letters), and monsters (8 letters). Spaceships are often used as a means of transportation for characters in sci-fi stories, while ALIENS, ETS, and UFOs are often seen as extraterrestrial life forms. Monsters are usually seen as creatures that are hostile to humans, and can be found in many sci-fi stories.