Mixcoatl was an Aztec deity, the father (according to some versions of the story) of Quetzalcoatl. The word literally means "cloud snake". Here's Mixcoatl dancing with Coyolxahqui, the goddess of the Moon, over Westwood.
It was indeed. This was clearly a jet contrail, but there were also plenty of other interesting clouds up there. I imagine it was the disturbed upper-air effects of the leading edge of the front that brought us thunderstorms on Wednesday.
We do get some weird contrails in SoCal - especially over the Pacific, most visible around sunset, many that are very erratic and couldn't possibly be made by commercial jets. Probably missile tests out of Vandenburg.