Here is some well known and not so well known trivia about TBC :

• The Library was actually a set constructed in the Maine North High School gym!
• The movie was filmed at Maine North High School, which is now an Illinois State Police Station!. It is located on Dee Road, Des Plaines.
• The football oval used at the end of the movie is located behind Glenbrook North High School.
• John Hughes actually graduated from Glenbrook North High School.
• There is no suburb called Shermer, nor is there a Shermer High School. The name Shermer comes from a street name (Shermer Road) which is where Glenbrook North High School is located..
• John Hughes made a cameo appearance as Brian's father who picks him up after detention
• Ally Sheedy was originally cast as Claire, and Emilo Estevez was originally cast as John Bender.
• The whistling marching tune in the movie is from the movie The Bridge On the River Kwai
• Carl the Janitor appears in the Man of the Year photo, obviously a former student!
• According to Anthony Michael Hall, Judd Nelson was actually the one to coin the phrase Neo-Maxi-Zoomdweebie (Thanks to CyberRam)
• Brians real life mother and sister play his mother and sister in the film.
• There is NO ending to the joke Bender says while he is crawling through the roof, rumour has it that Judd Nelson just made it up.
• John Hughes made the cast and crew eat their meals in the school caffeteria.
• The Brazilian title for TBC is "O Clube dos Cinco" which translates to something like "Club of Five" (Thanks to The FireByte)
• The classic John Hughes trademark of using a personalised number plate is also present in TBC - Brian's mother's car has the number plate "EMC2", which is of course Albert Einstein's classic special relativity equation. Very appropriate for a Nerds car!
• Another John Hughes film Ferris Buellers Day Off (my favourite!), has another number plate "TBC" which is of course The Breakfast Club.
• The term "The Breakfast Club" came from John Hughe's neigbours son who's school detention was called "The Breakfast Club"