I do spot these mistakes and it is quite funny sometimes.
The Wizard of Oz was peppered with them, Dorothy's hair changes length, as she and the Straw man and Tin man dance down the road, you can see in one of the scenes that the men have swapped sides on Dorothy's arm, so the film had to be cut out and put in the other way around.
This is noticable as the film is laterally inverted.
Ben Hur and the contrails in the sky was a fuuny one too.
more recently in 300, I noticed the shields kept changing size, they were smaller in the battle scenes...
Still, all these mistakes help me keep a grip on reality
Oh, and in the Mummy, did you notice the train stopped outside Luxor temple exactly where the Nile would have been, if they had bothered to research the area.....
