The Alien Sequel that's not Aliens
For those who thought James Cameron's Aliens was too exciting and high-budget, there was a completely unauthorized sequel to Alien made back in 1980. 20th Century Fox, upset at this obvious ripoff, reportedly tried to sue the filmmakers, but they argued that it was based on a 1930 novel called Alien. It was a weak case and everybody knew it, but we guess the judge was impressed by their moxie or something, because it worked. Alien 2: On Earth, also known as Alien Terror, is an ultra-violent, low-budget horror movie that finds the titular alien coming to Earth because, well, spaceship sets are expensive.
Alien 2 starts off with some folks exploring a cave -- naturally, this being an Italian film, just because they're in a cave doesn't mean things can't get randomly and inappropriately sexy.
This must be one of those cavern key parties we keep hearing about.
Finally, after some good, deep spelunkin', a member of the group is attacked by an alien. Here's what that looks like on a budget made of good intentions and spaghetti sauce: