14 Movies You Didn't Realise Stupidly Broke Their Own Rules

2. Don't Meddle With The Timeline - Back To The Future

The Rule

"Great Scott! Don't interfere with the time line, it can be catastrophic!" Making even the slightest change in the past can have apocalyptic results in the present, like turning a rape-loving, sports-gambling-cheating, manure-hating bully from inexplicably beloved family servant to megalomaniac, murderous despot.

But Wait...

The rules apply right up until the point when the old man who was previously uber-committed to the preservation of the timeline, suddenly wants to knock bones with the Wild West teacher lady.

At that point, rules be hanged, your fate is what you make it.