1.Cameron's father's Ferrari wasn't a real Ferrari. Because it was too expensive to rent one, they made three fake ones, each with a fiberglass body.
2.Early drafts had Ferris having two additional younger siblings. When it came time to edit, the final draft actually has evidence that Ferris in fact does have younger siblings, such as drawings on the fridge and a family photo seen in his dad's office.
3.The shot of Ferris playing the clarinet was done on the spot. Someone spotted the instrument as part of the set and Broderick said he could play it, which of course he couldn't.
4.Polly Noonan, who plays the girl that Rooney sits next to on the bus wore glasses that were specially made by the prop department. The lenses distorted her vision so much that they made her nauseous.
5.Most of the license plates are all abbreviations for titles of films by John Hughes.
6.Cameron was based on someone that John Hughes knew in high school.
7.Charlie Sheen was recommended by Jennifer Grey after they did Red Dawn together.
8.John Hughes personally designed Ferris's bedroom, mirrored mostly on his own bedroom when he was in high school.
9.John Hughes told Ben Stein, (who has a degree in Economics) to present an actual Economics lecture in his scenes. Hence nothing Ben Stein says (aside from the roll call) is scripted.
10.Mia Sara beat Molly Ringwald to the role of Sloane Peterson, because according to Hughes she had elegance.
11.Alan Ruck was 29 years-old when he played the role of Cameron.
12.John Candy auditioned for the role of Cameron Frye, but producers turned him down fearing he was too old for the part.
13.The Ferrari was originally supposed to smash through the window of the garage and land in the backyard. It over-shot its mark though and hit a fence that was dividing the house from the yard next door.
14.When Ferris hacks into the school's computer to change the number of absences he had, it is a subtle reference to a scene in WarGames when 'Matthew Broderick' hacks into the school's computer to change his grades.
15.The final scene in the garage was shot in early Fall, so each of the leaves on all the trees outside had to be hand-painted green every morning before shooting.
16.During the parade several of the people seen dancing originally had nothing to do with the film. They were simply dancing to the music being played and John Hughes found it so humorous that he told the camera operators to record it
17.To produce the desired drugged-out effect for his role as the drug addict in the police station, Charlie Sheen stayed awake for more than 48 hours before the scene was shot.
18.The hall scenes in which you see Jeanie walking down the hall and kid collecting money to save Ferris are the halls from The Breakfast Club.
19.Cindy Pickett and Lyman Ward, who played Ferris's parents, married in real life after filming this movie.
20.Rob Lowe, John Cusack, Jim Carrey, Johnny Depp, Tom Cruise, Robert Downey Jr. and Michael J. Fox were all considered for the role of Ferris Bueller.
21.Matthew Broderick felt that the film didn't need a sequel, that this film was about a specific time and place that we'd all like to revisit and didn't need updating.