The main eight actors were required to live in an apartment together for three months before filming (the actors unanimously say the worst cook of the bunch was Michelle Yeoh). Cillian Murphy's wife was pregnant during this time, so he would go back home at night. This proved helpful for his character being the youngest member and an outsider to the crew. The voice of the spaceship, Chipo Chung, was usually somewhere on the set and would be directly talking to other members of the cast, which is very appropriate for the character she's voicing.
Also in the scene where Capa falls over in the very heavy gold spacesuit and struggles to get back up, unbeknownst to him several stage-hands held him down while he was inside the suit for the internal shots, in a attempt to make his struggling look more realistic.
Fake Nationality: A few, but English Mark Strong plays Pinbacker, who is either of French or South African origin.