Alien was inspired in part by Dark Star
Dan O'Bannon, who worked on and starred in the 1974 SF classic film
Dark Star took the segment on hunting down their "pet" alien beach
ball and turned it into Alien.
And apparently the makers of this 1958 SF film sued the makers of
Alien for stealing their idea - though one does not have enough fingers
and toes to count the number of SF stories about a monster alien
terrorizing the crew of some spaceship:
http://en.wikipedia.org/wiki/It!_The_Terror_from_Beyond_Space
I remember seeing this film on television as a kid and I thought it was
pretty scary. This was back in the day when they used to show those
great cheesy SF flicks of the 1950s on a Saturday afternoon.