I'm counting Pluto as one of the nine planets. A cat has nine lives. Sudoku has 9 squares. Navratri is an Indian festival honouring Goddess Durga in nine different incarnations (translates to 9 nights) There are nine Navagrahas (seven celestial bodies in Sanskrit) that have an impact on Indian astrology. In Dante's Divine Comedy, there are nine circles of hell. There are more stuff