In the book, Patrick and Mary Elizabeth were chain smokers. That detail was removed in the film, likely to score a PG-13 rating.
Although never explicitly stated in the film, Sam’s full name is “Samantha Dutton” as shown on her SAT results.
Unlike in the film, the name of Charlie’s sister and brother is never mentioned in the novel.
When Patrick holds up his report card, the name at the top says “Patrick Nothing”, a reference to his nickname in the book and the film.