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).
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.
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.