The movie: When Stone opens the airlock to the ISS, she hastily removes her spacesuit to breath properly and relax after the rough journey. The audience is treated to a lovely shot of Sandra Bullock's super-fit body in tiny briefs and a tank top. Daaaaynm, girl.
Real life: Sadly, astronauts are not wearing skimpy little outfits under their spacesuits. They're wearing diapers. Yup, if Cuarón wanted to be really accurate, he would have made Bullock wear a Liquid Cooling and Ventilation Garment (pictured), which is a complex unitard designed to regulate body temperature and other vitals. Even the diaper part is given a fancy scientific name: "Maximum Absorbency Garment." Because what are you going to do, just pee in the leg of your spacesuit? Though that shot of Sandra was gorgeous, in real life we'd be more likely to see a very sweaty lady in soiled long underwear.