Trivia: Mare Winningham, whose storyline revolves around the fact that she's a virgin, was pregnant throughout the filming of the movie. This is the reason she's wearing those baggy clothes.
Trivia: Ally Sheedy was mortified after learning that she had to perform a sex scene as she presumed that it would be offscreen and simply implied. Director Joel Schumacher convinced her to do it by agreeing to only shoot her and Andrew McCarthy from the neck up. Also the scene where she accidentally pushes the shower screen down was unscripted and McCarthy's laughing reaction was genuine.