The "Quality Cafe" that appears in the movie is also featured in several other movies including Training Day (2001), Ghost World (2001), and Se7en (1995).

When Mitch (aka "The Godfather") comes home early, there is a bowl of oranges on the table. In The Godfather (1972), oranges are in scenes where something bad is about to happen. In this case Mitch is about to discover his girlfriend is cheating on him.

The foul-mouthed band playing at the wedding is a real rock band, called The Dan Band.

Dean Pritchard (Jeremy Piven) calls Sara Tanaka's character, Megan Huang, "Chang." The same mistake happens to Tanaka's character Margaret Yang in Rushmore (1998).

In the birthday party at Bernard "Beanie" Campbell's (Vince Vaughn) house, the fraternity recruit "Spanish" (“Rick Gonzalez”) is wearing an Eleroo costume. Eleroo was a character in the 1985 Disney cartoon "The Wuzzles" (1985).

The beer that Frank (Will Ferrell) drinks during the Mitch-a-Palooza scene is an O'Doul's (non-alcoholic).

The last scene shot was Mitch-a-Palooza.

Vince Vaughn had to keep the crowd at the Mitch-a-Palooza scene (over 300 of extras) under control by entertaining them for at least an hour.

The wedding scene where Mitch makes a speech was added during filming and the idea came from Vince Vaughn.

Vince Vaughn signed his contract for the movie during the scene with the wedding. It was his first day of shooting and he had to sign the contract before he could start.

Some of Luke Wilson's scenes (like when he arrives home) were done in one take. The crew nicknamed him "One Take Wilson."

The birthday party scene where Frank shoots himself with a tranquilizer gun and falls into the pool mimics a scene from The Graduate (1967). It includes the same camera angles and music ("The Sound of Silence", Paul Simon).

During the KY Jelly wrestling scene, the two female wrestlers are announced as residents of Hayden Hall. In reality, Hayden Hall is a dorm at director Todd Phillips's alma mater, New York University.

Blue's real name is Joseph (Jay) Pulaski. The Toronto Blue Jays have a minor league team named the Pulaski Blue Jays.

Director Todd Philips thought of this movie as a comedy version of Fight Club (1999) and as such there are several references to Fight Club in Old School. References include (but aren't limited to): the basement wrestling match, the photocopying of club propaganda at work, the men appearing worn at work, the restaurant scene, the behavior of the men during the initiation phase and Beanie’s outfit during the initiation scene is mimics Tyler Durden’s.

Director Cameo: Todd Phillips shows up at the door to ask about the gang bang.

Cameo: Stuart Cornfeld, Ben Stiller's producing partner, appears as the cab driver who takes Mitch to the airport.

The man who played Marissa's father and gave her away at the wedding is Will Ferrell's accountant.

Director Todd Phillips’ dog has a cameo in the movie as Garry, the oral sex instructor's dog.

Anthony Begonia auditioned for the role of Spanish.

Breckin Meyer has an uncredited role as a Highway Officer in the deleted scenes available on the DVD. Meyer previously starred in Road Trip, also directed by Todd Phillips.

The elephant suit that Spanish is wearing at the birthday party is the same outfit as the one in The Sweetest Thing.

The song "Here I Go Again" by Whitesnake is played four times in the movie - twice with the words, once without, and once hummed. The band Whitesnake is also mentioned by Mitch when he references Nicole's high school jean-jacket. Frank also wears a Whitesnake t-shirt at the very end of the movie, during the credits.