Shared with you
Whenever Mark boots up a computer (ie. when finding the MAV) a sequence of source code is seen appearing on a screen. The code is written in PVS (Prototype Verification System), an experimental macro language which NASA actually uses and it's very plausible to appear on a future spacecraft. This particular chunk of code is from the already existing NASA PVS Library, and you can find that very piece of code as open source if you type a part of it into Google.
Rich Purnell slips and falls after he finds a way to rescue Mark Watney and tells his boss "I need more coffee." Donald Glover revealed in an interview that he slipped for real and just got up and continued to act, and the footage was retained in the final edits for the movie.
Matt Damon admitted that the scene where Mark was getting emotional upon hearing Commander Lewis' voice was genuine. The other actors had wrapped and gone home, and their pre-recorded voices were actually being played to Damon from inside his spacesuit. When Damon began to think about how his character had been all alone on Mars for two years, alongside how he was only hearing pre-recorded voices of his co-stars who had already finished their scenes, he began to tear up. Sir Ridley Scott was so impressed with Damon's performance, that he only did one take of the scene, which was used in the film.
A real potato farm was installed on the studio lot with potatoes in all stages of growth so they could be used for filming.
Sir Ridley Scott claimed that Matt Damon's solo scenes were shot for five weeks straight, after which Damon was relieved from the schedule. Consequently, Damon did not see most of his co-stars again until the cast was reunited to promote the film.
NASA was consulted in order to get aspects of space and space travel, specifically in relation to Mars, with the most accuracy. NASA is federally funded, yet charges no one, including private for-profit organizations, any fees for use of and access to its archives and consultancy.