Continuity mistake: The alien's spaceship falls from the sky and crash in the ground with its bottom facing one side. It rolls to Meredith Vickers and Elizabeth Shaw. But it faces the other side after crushing Vickers.
Continuity mistake: Upon entering the alien ship, Shaw can be seen holding a single-bulb flashlight, right after Fifield begins howling as he releases his "pups". But later on when Holloway notices the CO2 levels, she is holding a triple-bulb flashlight.
Revealing mistake: When Shaw goes to the med pod for her emergency surgery, as she quickly taps on the entrance door to the med-pod room, on the left-hand side of the frame you can see the door is already partially open and then opens before Shaw has finished typing in the code.
Continuity mistake: After Elizabeth tells Janek the engineer is headed for Earth and it needs to be stopped, Vickers shouts to Janek, "Captain, let's go." Janek is then shown looking downwards with his lips clenched shut and his eyes are clenched a bit. In the next shot, his mouth is suddenly open and unclenched, looking straight forward with no time to do so.
Other mistake: Charlie gets up and goes to the bathroom, where he finds a sink full of water ready for him, although he didn't ask a machine to do it and he didn't fill it himself.
Other mistake: When Dr Shaw is in the medical "machine", and she wants an abdominal operation, a voice says, "Preparing anaesthetics," but all it does is wipe a line on her stomach with something brown - could be betadine. But Shaw screams and yells in pain. If it really is a "machine" that can perform surgery, well, surely it could put the patient under an anaesthetic that knocks them out, properly.
Answer: It's a matter of opinion, but watching the first Alien film gives enough of the necessary back story to understand Prometheus. However, it's possible to watch and understand Prometheus without seeing any of the other four Alien films. I would only recommend watching Alien 1 and 2.
raywest ★