The ending (spoilers)
Does anyone know if the ONLY post-production change was the adding of lasers coming from the monster's eyes? If so, the ending of this zombie movie involves it having the ability to throw people against a wall from 20ft or more away, and to be dispatched by being set on fire by Devane. I have never heard that zombies are combustible and can be killed this way - that was highly unconvincing, and bordering on ludicrous.
If they went back and reshot the ending, why not add a scene at the start that explains how the alien got to be wearing Earth clothing? Even hinting at possessing a human body, along the lines of "Invasion of the Body Snatchers" would have done as a basic explanation.
"I am big. It's the pictures that got small."