The fact that movies are such huge productions with so many different people and departments working on them means that occasionally mistakes slip through the gaps. This is a simple fact that has always been true as it is almost impossible to catch every single error as those in charge only have a limited amount of time to look at every single detail. However, sometimes there are mistakes that make it into the final edit that fans simply can’t believe because they are so ridiculous or important.
Although the giant shark that kills Quint isn’t exactly the most realistic looking model ever used in a film, it isn’t that which spoils this scene. It’s the large pillow that is clearly visible below the character, destroying any illusion of danger and jeopardy.
Although it has since become something of a meme due to the sheer stupidity of the mistake, it is still amazing that this particular error managed to make it into the final edit of the movie. While the Stormtroopers are marching through the Death Star one of them very clearly walks into a door that hasn’t fully opened.