The obvious movie fake, for me, is in WW2 movies which have lots of old British cruiser tanks badly disguised as panzers by the cunning ploy of painting a black cross on the turret.

And not fakery, as such, but I do tend to notice birdsong on the soundtrack, and often as not it's from species that are not supposed to be in the relevant part of the world. In television SF, that means the relevant planet.