From Cracked
If all movies followed the same physical laws as the real world, they wouldn’t be a lot of fun — we don’t want action heroes to break their legs every time they jump off a bridge and into the top of a speeding truck, we want them to roll over painlessly and continue with the chase scene (or, alternatively, to explode for no reason).
However, once you’ve established the rules of your movie universe, the only thing we ask is that you follow those rules. Don’t say that your time traveling robot unicorn is powered by ice cream in one scene and blowjobs in the next. That’s just sloppy writing.
Banana Scoop 
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