No body doubles were used in any of the sex scenes.
Upon seeing the film, Steven Spielberg noticed Wayne Knight, and immediately wanted him to play Dennis Nedry in Jurassic Park (1993). He stayed through the end credits just to find his name, and Knight ended up being the first actor cast.
Sharon Stone was director Paul Verhoeven's first choice for the role of Catherine Tramell, but he said that it took him about 3 months to convince the studio, his producers and main star Michael Douglas that she would be best for the role, as she was not a marquee name at the time. Stone was only offered the part after thirteen actresses had turned it down due to being uncomfortable with all the nudity.
Paul Verhoeven had some disagreements with Michael Douglas over his direction of Sharon Stone. Stone was reportedly very nervous and insecure, and in her first scenes, she was unable to replicate the performance that she had given during her audition. According to Verhoeven, she came very close to being replaced, but since he knew she had what the role required, he coached her intensively to get the required performance out of her. However, this caused Douglas to feel left out, as Verhoeven thought that Douglas, as an established actor, no longer needed such close attention. It eventually lead to a very heated argument in a trailer, the stress of which caused Verhoeven to burst a vein in his nose that caused profuse bleeding. When he went outside with blood-stained clothes, crew members believed that Douglas had physically hit him in the face.
Michael Douglas felt an established star was needed to play Catherine, so the movie would be carried by two well-known actors, and the risk of career damage would also be shared. He suggested Demi Moore or Michelle Pfeiffer for the part, but no actress of name was prepared to go completely nude for the role. Pfeiffer said she found the idea of filming the erotic love scenes too daunting. "I just couldn't do that one, because of the sexual parts, the nudity," she's said. "My father was still alive. I'm kind of prudish. And honestly? I am not that uninhibited about my body. I'm modest."