The adult alien is, believe it or not, a giant penis.
H.R. Giger’s iconic creature design for the film’s homicidal adult alien remains a work of pure genius. Just look at it—all teeth, with skinny, manlike legs and a reptilian disposition, the imposing figure is devoid of any eyes, erasing any and all chances of earning its sympathy or reading its emotional state. It’s solely out to kill, and its acid blood doesn’t help its victims’ causes.
But take a closer look at the alien’s head—what does it resemble? What’s long, has a hole at its end, and a fiery liquid when provoked? We’ll let Alien star Sigourney Weaver supply the answer, courtesy of a quote from Ian Nathan’s Alien Vault book: “I remember when I first saw the sketches… I thought, ‘This is a giant penis!’”
And Giger, in philosophical manner, doesn’t deny the sexual innuendo. “Any object has sexual symbolism,” he says in Alien Vault. “I hate violence but violence can be played out in sexual play.” So, yeah, the big skull (attached to that ghoulish frame) that looks like a wiener, was born from a man’s chest, and hunts down a lonely, scared female is, in a way, a creepily phallic metaphor. Sigmund Freud, be damned.