Movie Mistakes Reveal the Lie

I have always had a fascination with mistakes in movies with continuity errors (items switching positions between shots), equipment or crew visible (either clearly like in Harry Potter, or in reflections), factual errors (later era planes or ships used in a period piece), to downright illogical use of the surroundings (flat land suddenly becomes a large drop-off in Jurassic Park). Since I took a class on film in college, I have a better understanding of how it came about that these errors have occurred. The Lord of the Rings trilogy flipped the screen a lot, which most of the time is not noticeable because the human body is symmetrical (the same on either side). But when you have a leaf on your cloak that points one way, it becomes painfully obvious. The reason for doing this is the camera angle shows them looking one way. Another shot has them looking another way, but if you flip the image, it makes it look like they are looking in the same direction.