Creator Backlash: Minor example. Emma Watson says she refuses to watch her kissing scenes or the Rocky Horror scene.
Dawson Casting: Averted with Ezra Miller as Patrick, who was 18, but played straight with 21-year-old Emma Watson as a high school senior. Logan Lerman was eighteen, two years older than his character. Also Lerman is nine months older than Miller, who plays a character nearly four years his senior.
Playing Against Type: Melanie Lynskey is generally known for playing quirky characters. In The Perks of Being a Wallflower she played the main character's aunt, a child molester who abused the protagonist and later died in a car crash.
John Hughes originally had the film rights and planned to make the movie more as a dark comedy. Shia Le Beouf would have played Charlie, Kirsten Dunst as Sam and Patrick Fugit as Patrick. However his sudden death meant that the project was shelved, and eventually made as an independent film with the original author directing.
A subplot involving Candace telling Charlie she is pregnant and going to get an abortion was filmed, but cut from the film to avoid an R rating.
Alice being a lesbian was cut from the original book.