Not sure about the Fallen. I'd hesitate to say they were inspired by the Sangheili because they are a pale shadow, comparatively speaking. I would say the Hive came from their original fantasy concept of an undead army, which they then adapted to a Sci-Fi environment. For the Cabal, I cooked up a [url=http://1.bp.blogspot.com/-XXX-AP9eMvU/Uh5Mje7vB-I/AAAAAAAAAJU/cU_uJlGdSyg/s1600/cabalorigin.jpg]visual aid[/url] a while back to illustrate my theory. As for the Vex I'd say that, after coming off of a week-long bender with some hard-partying Cylons, Skynet got pregnant & had the brilliant idea of making a bunch of babies with triceratops heads.