I have watched this movie on Vietnam Central Television (VTV1, "The Little Flowers" program) since I was very young, of course only on black-white TV. This is a very challenging movie about translation. Here is the film story (фильм-сказка) : http://www.barius.ru/biblioteka/book/852

Nice book! Thanks for that link.

Yes, I found it hard to translate as well. But if you're trying to do it, I think you should use the latest English subtitles that are here, rather than the older ones elsewhere online (a lot of which have mistakes).

By the way, regarding the names of the characters:
(Professor) Selezniov = slug
(Captain) Zelyony = green
Gromozeka = the root is "grom" (thunder), probably because of how boisterous he is
Veselchak = happy person (he's often smiling and eager to please in the film)
(Professor) Verhovtsev = higher
Ptitsa Govorun = talkative bird (I was fortunate that English already has the word "chatterbox", which I could easily modify into "chatterbird")
Glot = possibly from "glotka" (throat)

Most of these I kept as is, but I did translate "Green" because that's a common English surname too.

In my opinion, that is fine to leave most of it as is, just footnotes. However, fortunately characters "Veselchak U" and "chatterbird" have equivalent words in classical Vietnamese language : Tễu (笑 / "laugh" ; who has a cute body and funny personality), Liến Thoắng (連通 / "continuous communication").

https://tve-4u.org/threads/alisa-phieu-luu-ki-kir-bulychyov.36569/