Planet X is the name of planets in multiple works of science fiction and popular science. Perhaps the penultimate in uncreative planet names.
List
- Isaac Asimov's short story "The Deep," in his collection The Martian Way
- Paul Davies' nonfiction The Eerie Silence
- (Desert Planet) - Buzz Lightyear of Star Command
- Leather Goddesses of Phobos 2 video game