Cars and stand-ins
How many times did you notice cars driving in the background? I'm half way through the blu ray and up to six so far.
And how about Heston's stand-in with different colour hair?
There's also a man walking on the right side sidewalk in the opening scene when Neville is driving down the street, and the camera is panning down following his red car.
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Every person that served can be called a veteran, but not every veteran can be called a Marine.