The symbols of the Country of Unknown Fathers are very similar to those of the Hungarian national socialist Arrow Cross Party, which is probably due to the fact that the names used on the planet of Saraksh both in the film and in the original novel are based on Hungarian-language names.
Hans Zimmer was to have scored the film, but when the first edit of the film was sent to him, it turned out his schedule could not fit with the post-production schedule. The film was scored by Yuriy Poteenko in the end.
Director/producer/actor Fedor Bondarchuk regards the role of Procurator as the best role he ever played. On the other hand, he said in an interview that he was so outraged by Vasiliy Stepanov's bad acting that he had a nervous breakdown and recovered only about 18 months after the filming. Stepanov's acting was so bad that the editors had to combine many cuts when editing the film, Bondarchuk also said. Stepanov, who was not yet even a theatrical school student when he got the part, admitted himself that "the crew had a tough time with [him]" and avoided a straightforward answer when asked if he thought whether the film was good.
Boris Strugatskiy, one of the authors of the original book, who did not write any scripts after his brother and co-author Arkadiy Strugatskiy died in 1991, refused to script the film but when Marina Dyachenko and Sergey Dyachenko, also Sci-Fi authors, were hired, he said, "They can't write a bad script." According to Fedor Bondarchuk, there were 28 versions of the script, all of which "were very close to the Strugatskys' text".
Vasiliy Stepanov and Pyotr Fyodorov had to work out a lot to prepare for their roles. Fedor Bondarchuk recalls that he gave Stepanov a gym subscription and told him to "look like Apollo after six months." Stepanov started training before Fyodorov and became so massive Fyodorov didn't believe it was Stepanov at first when he came to the same gym and saw him. Later on, Stepanov and Fyodorov trained together and Fyodorov, too, gained 20 kilograms. Yuriy Kutsenko was also amazed to see Stepanov after training, saying he wanted to become an action hero again.
Yuliya Snigir, who was one of the last actors and actresses to be cast, compared her role and other roles from the film between the book and the script and kept asking director Fedor Bondarchuk about the point of the differences. She thinks it outraged him so much he "was ready to kill" her at that time.