Here's some creepy test footage from Ridley Scott's Alien featuring Bolaji Badejo who played the Alien in classically badass 1979 sci-fi horror masterpiece. In the footage you see the actor practicing his alien movement skills without the full costume. All he's wearing is a pair of shorts and a prop Alien head. It's still creepy even without the costume though!
Here's what Badejo had to say about the costume he wore in the film in 1979 in an interview with Cinefantastique magazine,
[The special-effects helmet] was all manual, remote controlled [...] There's still a space in it for my head. I had it on just to make sure nothing goes wrong with the posture of the head or how tall it is in comparison to the other sequences. They must have had about 2000 tubes of K-Y Jelly [...] just to get the effect of that slime coming out of his mouth. A lot of it was spread around on the face. I could barely see what was going on around me, except when I was in a stationary position, while they were filming. Then there were a few holes I could look through.
Check out the Alien test footage below. We don't make movies like this anymore.