"Revenge of Billy the Kid" is a very facetious, Troma-esque horror-comedy that should appeal to anyone with a taste for disgusting shit-humor and creature films.
A disgusting, pugnacious farm family's goat is drying up her milk supply so daddy takes the animal out into the woods and is drunkenly over-come by bestial lust - resulting in an abominable mutation. The only one to love the human/goat half-breed creature is the daughter who treats it like a pet. That is, until the creature, Billy, trashes the dad's home-made liquor stock pile and get's it's ass tossed in a gunny sack and discarded. Sure enough, though, the thing comes back bigger and madder than ever and begins killing off the despicable family members...
While this film has it's share of whacky, juvenile 'gross-out' comedic demeanor, it DOES drastically shift into a rather straight-forward 'creature film' horror climax upon Billy's big return. This is good because, as much as I enjoy a good goat fucking gag and a dirty drunk hick having noisy kitchen-sex with his morbidly obese, corncob pipe sporting wife - the "humor" DID get a bit repetitive what with the constant dubbed in fart noises and exaggerated slob behavior. The creature effects of Billy are decent enough - if not just a little bit silly considering how massive it's head is and there's a tolerable amount of gore thrown in, but nothing to really write home about.
If you like crude horror-comedies, "Revenge of Billy the Kid" isn't the very BEST you can do, but I'd recommend it for the neat creature and a few, previously noted, 'key' scenes.