

Dan Obannon (with Ron Shusett) wrote the screenplay for the original Alien. On every Alien movies since you will see his name in the credits...but 'Alien' wasn't the only one - he wrote one other epic scifi movie - Lifeforce.
It's insane in parts and unlike any other movie ever made, but if you are a fan of the Alien universe (particularly the Ridley Scott material) then you will recognise themes and even entire plot pieces in lifeforce - you will get a huge deja-vu feeling. There is definitely a creative connection here. Dan Obannon was one crazy twisted genius.
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Yup, that's the one!
Another connection: Texas Chainsaw Massacre was influential to Scott in inspiring some of the horror aspects of Alien. Both Texas Chainsaw and Lifeforce were directed by Tobe Hooper.
BZ

@Glenn R - I remember seeing that one in the theater in 1985! It was TriStar's first movie, if I remember correctly? Of course, that was 1985!