My girlfriend turned to me after watching Magnolia and went '...I got most of the film but I didn't understand the two timelines.'
She thought Donnie Smith was the older version of the Stanley the quiz kid and Earl Patridge was the older version of Jimmy Gator. Thus when the frogs arrived not only did that not make the sense but the fact it had happened twice to the same characters 20 years apart...
What's the stupidest misunderstanding of a film have you heard of?