During the final football game, when the Guardians defeat the hotshots from the Financial District, the tone of the narration seems intended to imitate John Facenda of NFL Films (in a tongue-in-cheek manner).
Kate Winslet was so impressed by In the Bedroom (2001) that she was determined to work with Todd Field. She said the movie made her feel very uneasy, and was intrigued by the director responsible for that.
When Ronnie goes on a date with Sheila, she mentions 'being like her sisters and having lots of kids'. In Todd Solondz' movie 'Happiness', she plays a neurotic, unlucky-in-love woman with sisters with kids. It is very much the same character.
The trivia items below may give away important plot points.
In the novel, the character Ronnie bears very little physical resemblance to Jackie Earle Haley, being an overweight, balding chain-smoker who wears glasses. The novel makes the character even less likable and confirms that he was a child-killer.
In the novel, Richard (Gregg Edelman) goes to Southern California to meet Slutty Kay (Sarah Buxton). Richard's story line all but disappears half way through the film, but seems likely that this later interlude was shot.