system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: When movies that include a different species that speaks a made-up language, do the directors/producers actually "create" a new language? Do they create a base of words and translate from that? Or is the made-up language completely improvised?
gpt
There are a few ways to go about this, usually depending on how much the language is going to be used on screen. Usually, it's not improvised on the spot so that it sounds something like actual language between two people.

Greedo's dialog in Star Wars was recorded in French, then played backward in the movie.

James Doohan (Scotty) wrote the dialog for Klingons in the first Star Trek movie; it's completely made up, but written to sound consistent. Usually when this happens, some words are made up to replace words used in the speaker's native language so it's easier for the actors to remember.

In the third movie, Klingons are on screen a lot, so linguist Mark Okrand was hired to make a language for them to speak which has been used for their appearances since then. In turn, fans were able to use his basic syntax rules and vocabulary from the films to create a usable language. Another linguist, Paul Frommer, did the same thing for the Na'Vi language in "Avatar."