An amnesiac cowboy who is lucky he has forgotten his past ends up on the wrong side of the law. Meanwhile there's an alien invasion happening.
A clever way of getting the traditional population of a western: outlaws, indians, the sheriff and assorted townfolk all working on the same side. Sumptuously photographed with compelling effects but as insubstantial as a tumbleweed.
You can't just come up with a clever movie title. . .you actually have to have a clever script, too. Especially true if you're going to make the movie two hours long.