In the truth or dare scene, when asked about his fantasy, Rocky says he fantasized about a girl named Susan Johnson (at around 41 mins). One of the producers of the film is called Susan Johnson.
The names that Martini (Marty) says during shooting practice are all names of various cast and crew members: Mr. (Hagai) Shaham (producer, actor - Handsome Police Officer); Mr. (Jacob Aaron) Estes (director, screenwriter); Ms (Susan and Joan) Johnson (producer and production coordinator); Mr. (Rick) Rosenthal (producer).
The bumper sticker on the back of Marty's mom's car reads "My child kicked the crap out of your honor student."
Mean Creek generated controversy due to the scene in which the character Mille uses a penknife to stab a live snail to death. It is unknown if the snail was indeed real or alive at the time, or if the scene was staged.
When Rory Culkin tries to coax Trevor Morgan to call off the prank, we eventually see 'Josh Peck''s character interrupt him and then scratch his head (at around 28 mins). Scratching his head was Scott Mechlowicz's cue to say his line.
Trevor Morgan and Rory Culkin were both previously directed by M. Night Shyamalan in The Sixth Sense and Signs respectively.
The stickers on the Merricks door toward the end of the film say LDS and CTR. LDS stands for Latter-Day Saints which is short for The Church of Jesus Christ of Latter Day Saints, or more commonly known as "mormons". One of the most common mottos that Mormons teach their children is to "choose the right", which is what CTR stands for. Mormon children are commonly given rings and stickers and other branding with CTR to help them remember to always "choose the right" when faced with tough decisions.
In this film, Ryan Kelley's character is bullied as being gay (though he's not) just because his parents are a gay couple. Later on, Kelley played a character in Prayers for Bobby (2009), who faces prejudice for being openly gay.