I think you'll find as Buddhism assimiliated into native cultures, and due to it's non-fundamentalist nature, it left plenty of room for such concepts. Tibetan Buddhism is particularly rich in pre-Buddhist mythology. However, they are not central to Buddha's teachings, and believing in them is not a requirement. My favorite sect is Zen Buddhism, so I tend to represent this interpretation. They are free of theistic concepts.
Ah, I didn't realize that. I kinda learned what I know about Buddhism from my art class, so it probably made these themes disproportionately important. Does the same hold for reincarnation?