Corrected entry: If you watch the scene where the Gremlin is throwing plates at Billy's mother in slow motion, on the last plate thrown, you will see that the plate is not in the gremlin's hand, rather it comes up from behind the gremlin.
Corrected entry: The movie takes place in winter. With all the snow on the ground wouldn't the snow cause the gremlins to reproduce due to the water content. Even in Dory's bar, the gremlins spill beer and other drinks on themselves, don't those drinks also contain water?
Correction: The majority of liquids we consume contain some water. I think water must be fairly pure to make them reproduce, otherwise mogwais would either die of thirst or reproduce every time they drank something (liquid touching lips would cause reproduction).
Corrected entry: The town of Kingston Falls is covered in snow the entire film. And it's established that water makes the mogwai and gremlins reproduce. but throughout the film, we see gremlins moving through the snow on at least several occasions without becoming wet and sprouting more gremlins. We even once see a gremlin submerged in snow, and still - no new gremlins. The film shows that only a few drops of water will sprout a new one, so it just doesn't add up. You could argue that gremlins might be cold-blooded, and thus wouldn't melt the snow enough to get wet, but this would contradict the several moments on-screen where gremlins go from inside warm houses and buildings directly out into the snow - where residual heat should melt the snow and produce more gremlins. Just another example of the whimsical rules not quite adding up under scrutiny.
Correction: In the original script it was mentioned they could only reproduce at certain temperatures, but it didn't make it into the final film. Just because the concept of why snow doesn't cause them to multiply isn't in the film doesn't constitute a mistake for fictional creatures. Even if the snow melted, the water could still be too cold to cause them to reproduce.
Correction: If you have to use slow motion to see this, it is not valid as a mistake.
Twotall