The actors all had to live together in order to create a palpable feeling onscreen that they all knew each other (Cillian Murphy was given dispensation to go home every night as his wife was pregnant at the time).
Danny Boyle was so impressed with Michelle Yeoh's audition that he told her that she could choose any part in the script and he would give it to her - he was even prepared to change the gender if she had chosen a male character. She ultimately decided on Corazon, the biologist.
Kaneda, the captain, was originally written as an American, but scientist and space experts persuaded Danny Boyle to change the nationality, to make it more in keeping with the international nature of space missions. Hiroyuki Sanada was recommended to Boyle by Wong Kar-Wai.
The distinctive golden color of the space suits was intended to make them memorable to sci-fi fans. The character "Kenny" from South Park (1997) was used as a design reference for the funnel-shaped helmet. A small number of suits and helmets were built as wearable costumes, so the actors could experience the claustrophobia and react appropriately.
The plot does not revolve around the sun dying in the normal sense: this is not due for around five billion years based on our understanding of nuclear fusion. It has instead been "infected" with a "Q-ball" - a supersymmetric nucleus, left over from the big bang - that is disrupting the normal matter. This is a theoretical particle that scientists at CERN are currently trying to confirm, and was one of the many contributions of the science advisor. The film's bomb is meant to blast the Q-ball to its constituent parts which will then naturally decay, allowing the sun to return to normal.