I saw this in the theater the day it came out; I was 16 at the time. It was amazing, but I remember being a bit disconcerted at the fact that so many people brought their young children with them to the screening.

Now, here's a few fun facts that many people don't know:

1. The set of the USS Nostromo was a "closed" set; not in the traditional sense, but rather in that there was only one way on and off the set itself — through the main airlock. Ridley Scott purposely had it built that way so as to give the cast a sense of claustrophobia and realism.

2. The only room in the set dressed in white is the cryo chamber, and was an allegory for emerging from the 'innocence' of the womb.

3. The only actor who knew what was going to happen in the "chest-burster" scene was John Hurt. Scott specifically did not tell the rest of the cast in order to capture their actual reactions to what was going on in front of them. In particular, Veronica Cartwright's reaction is the most violent, and she has said she would never have been able to react that way had she known what was coming.

4. As has already been noted by another commenter (richardrae1), in the original lifecycle of the Alien creature itself, there was no Queen. The xenomorphs would capture prey, and implant something in the host that would feed on the host, turning it into the leathery egg. The eggs would remain dormant until activated by another life form when the face-hugger would burst out beginning the cycle again.

5. As true xenomorphs, the Alien creatures would take on characteristics of their host creatures; hence, in the film treatment of Alien 3, the creature runs much like a dog does, and also has the lithe build of a canine as well. While in the book, the Alien gestates in a cow, and has a very bulky, brawny build. Also, if you reference Prometheus, you see the first fully-mature Alien emerging from an actual host, it has many of the characteristics of its host.

6. Dan O'Bannon and Ronald Shusett said "Alien" was written as the antithesis to "Close Encounters of the Third Kind," which, they said, took the 'aliens are our friends' approach. They wanted to portray a totally ruthless alien creature.

7. In the book treatment for Alien, Jones the cat is described as "indestructible."

8. The gas Ripley uses in the escape shuttle to get the Alien out of its hidey-hole is clearly identified on the button she presses; if you freeze-frame it at the right moment, you can actually see what it is.

So there you go, a handful of fun-facts you can now use in your next movie trivia game!