I haven’t seen the movie, but “mom and pop” fries are almost never sliced as thin as fast food fries and generally tend to be more “potato-y” in the center. The water is not driven out as effectively in this case.
I’m surprised no one has related their personal experience with fry preservation- I’ve had fries from 3-4 different burger places sit under my car seat for years without growing mold. It’s nothing unique to McDonalds.
Wow, Got it in one!
Maybe they are so desicated they are, in fact mummified.
Just a BTW. Sugar, actually usually dextrose, is used to coat commercial french fries. The sugar caramelizes and therefore browns with heating, giving the fries the golden look that everybody loves.
And a confirmation of the fact that sugar itself doesn’t go bad because it’s hydrophilic and removes the water needed for bacteria to grow on. If you look at a container of salt you’ll see sugar as a second ingredient. Keeps the salt from clumping.
Sugar is great for preventing bacterial growth but, as a lab flunky and home canner, I can say that jams, jellies, and such do grow mold if you don’t seal them properly.
Oh, and fries arriving at restaurants are already partially cooked. The ideal fry is first blanched in oil at a lower temperature then later fried a second time at a higher temperature. My brother sells the things and could probably tell you so much about them it’d make your eyes glaze over. He did it to me.
So McDonalds’s “Apple Dippers” are coated with vitamin C (and maybe a little calcium thrown in for good measure) to prevent them from going brown, eh? I guess that makes sense – they do taste more tart than regular apples, to me anyway.
So how does the acidic coating keep them from going brown? Well, I suppose I can just look that one up myself.
As for the french fries, I also have had fries fall under the car seat or behind a bookshelf at home and stay there for years without growing mold or changing at all. The apples may be explainable by an acidic coating, but the french fries are clear evidence of Satanic dealings, I tell you! 
When apples and other fruits and veggies are cut, you break cell walls. Chemicals inside the cells leak out and mix with chemicals outside the cells, producing the browning. From what I understand. Acid prohibits these chemicals from reacting. I don’t know what these chemicals are, but that’s basucally the gist of it.
Maybe it’s the shortening that’s mixed in the “potato center” of the fry. That isn’t a pure potato slice, I believe they are processed and die squeezed potato mash…
That’s how some fries are made, but not Mc Donald’s. The shoe string potatoes are soaked in a sugar water/corn syrup solution, deep fried, then cooled and deep fried again. At some point in the process they are quick frozen, then deep fried again, then salted. I’d imagine after all that, there’s little remaining that germs would care to colonize.
Anything to report QED?
Well, they’re most definitely not going to decay any time soon. I assume the initial moisture content was just too low, since now the’ve all just dried up and are hard as a rock. FWIW, the cooked, salted one still looks good enough to eat. You’d break a tooth if you tried, though.