Back to the Future (1985)
The famous scene from Back to the Future where Marty McFly plays the guitar has a mistake in it. The guitar that Marty holds in his hands, which is a Gibson ES-345, was released 3 years after the events of Back to the Future took place. The film is set in 1955 and the red Gibson was released only in 1958.
As to Hagrid's parents, love will find a way, especially if one of them is a wizard.
BTW, I had a Korean friend who was incensed beyond measure that all the North Korean characters spoke with _South_ Korean accents in 'Die Another Day' — and even more by the villain's dad, who had a Cantonese accent.