Don’t let the title fool you.
There aren’t any aliens on display here. This is routine zombie stuff, notable only for the presence of a totally unrecognizable Buster “Flash Gordon” Crabbe as the Sheriff, and the curious notion that the lumbering undead ate all the alligators in the swamp before starting on the locals.
As slow as they are, however, that doesn’t seem to give them much trouble.
We do get a brief little flashback with something like a meteorite landing, and apparently infecting the people it hit. Or something like that. Let’s face it, The Night of the Living Dead offers a more cogent science fictional non-explanation than that.
Fred Olen Ray directed this one, which should be enough of a warning to keep anyone away. He doesn’t even bother to give it a proper ending: it just…