Noticing movie mistakes feels like finding out how a great magic trick is done. But as with an illusion, the way a movie is shot and cut tends to distract us from those flaws and most of the time we don't even see them.
Continuity is the consistency of what happens in the movie for a certain period. Everything that doesn't seem to match the character, the plot, or the environment is considered a mistake, unless, of course, it was deliberate. There are lots of videos that show famous movie continuity problems and instead of us despising those films, we are fascinated by the fact we didn't see any of those issues. Yeah, you were tricked and you liked it. In this video, This Guy Edits shows you exactly why you fall for those illusions.
Famous films are usually with budgets in millions and there's a member from the crew called a "script supervisor." Their role is to watch out for the continuity consistency such as how full was a glass of water the in the last scene, or where the bruise on the actor's skin was. Despite of that, we see mistakes. Is the script supervisor to blame? How come the director or the editor didn't see those mistakes? Most of the time they really do, but their decision to leave it there is based on using the the best performance take and such flaws are considered negligible especially if the scene is highly emotional and effective.
And if you still don't believe you can be easily tricked, watch the next video: