I’m not sure which movie you’re discussing here, but I’d like to bring up a distinction I have mentioned many times on this Board – from the 1930s until about the 1970s “android” was widely used in science fiction to mean artificial biological constructs, not living, but using non-metal parts (as opposed to Robots, which were basically mechanical people, largely built out of metal). Edmond Hamilton seems to be the writer who made the distinction, and propagated it through both his science fiction writing (such as the Captain Future series) and comic books (he write for Superman and other DC titles). The authoritative Encyclopedia of Science Fiction followed his lead, and the online version still supports this definition. *
Therefore you’d expect to have an android having arteries and veins filled with, if not blood, then some other fluid serving the same purpose. It’s the Robots that you wouldn’t expect to have fluid-filled conduits.
But in the late seventies things changed. I suspect it was due to two factors in 1977 – the death of Hamilton and the release of Star Wars, in which R2D2 and C3P0 are called “Droids”, which I suspect is a shortened form of “Androids”, influenced by the term “Drones” used for short robots in the film Silent Running (R2D2 and CeP0 actually ARE called Robots in one scene of the original Star Wars, and then never again in any of the Star Wars films, books, etc. , as far as I know). Ever since, “Android” has been creeping back to meaning "Man-Shaped automata, whatever it’s made of.
In the film Alien, which you might be referencing, (Spoilers!) Ash is ultimately revealed to be a “Robot”, but it’s a Robot with lots of non-metallic parts and filled with white fluid, so it’s not clear if he’s a classic Robot or a classic Android or some mix of the two. In the sequel Aliens (which you might also be referring to), Bishop is also revealed to be an android, also with gooshy parts and filled with white fluid.
So it’s not unreasonable to have an android/robot/whatever to be filled with fluid, although not human blood (although even that, I think, has been done).
- The term “Android” for human-shaped automata actually predates “Robot”. It was used in the 19th century, whereas “Robot” dates from Kael Capek’s play R.U.R. (1920), and is a shortened version of the Czeck word for “worker”. To make things more confusing, Capek’s “robots” are what Hamilton would have called “androids”, since they’re made of organic matter, and were portrayed onstage by human actors that weren’t trying to look like metal.