In Hopi mythology, Kachina are supernatural beings representing various natural forces and/or ancestral spirits. The term is also used for the traditional dolls and the ritual dancers depicting them. Advocates of the ancient astronauts
theory hypothesis meme have tried to use them as supporting evidence for alien visitation in the past, citing the "Kachina-as-teachers" myths and drawing a parallel between the Kachina masks and astronauts' helmets.
Several "prophecies" (or variants of a single one) attributed to the Hopi have been used to support various apocalyptic claims, such as the 2012 apocalypse.
In the 1950s, Benjamin Lee Whorf (the Whorf in the "Sapir-Whorf hypothesis") claimed that the Hopi language lacked the concept of time (had “no words, grammatical forms, construction or expressions that refer directly to what we call “time.”) He's wrong.
 See also
- Official website (yes, they do have one)
- Hopi prophecies, page at 2012hoax.org
- Page with purported Native American prophecies, including several Hopi ones