When Greg and Sandy walk to the house after jumping into the water, their clothes start out wet and when they get closer to the house their clothes are completely dry.
When the jellyfish-like alien lands onto the van's windshield that Greg and Sandy drive in, you can see the alien prop's residue already on the windshield before it lands on it.
At various points in the film, the alien flying discs can be seen being suspended from wires.
Inside the bar is seen a Mr. Coffee behind the bar. A real restaurant or bar would have a professional brewer and decanter, not a home version.