20 Things You Didn't Know About Alien 3
15. The Xenomorph Was Meant To Be Played By A Dog
In most shots, the Xenomorph is portrayed by a rod puppet - but there was a time where Fincher considered going in a very different direction. After the Xenomorph was born, there was meant to be a wide shot showing the newborn crawling around the room.
Because the crew couldn't figure out how to hide the puppeteer while shooting this scene, they concluded that there was only one way to film it; put a dog in an alien costume. One crew member brought in his whippet to the set, put him in a Xenomorph costume, and shot the scene. Unfortunately, the crew felt like the way the whippet moved made the alien look unintentionally hilarious and so they were forced to scrap this idea.
This shot was inserted into a remastered version of the film a decade later but CGI was used instead of a dog.