1. Ferris has a security camera rigged in his room.
2. Ferris changes nine times before ever leaving the house.
3. The Ferrari's license plate reads "NRVOUS."
4. And all the other license plates are nods to director John Hughes' earlier films.
5. Another nod to a John Hughes movie — Ferris has a poster for Simple Minds' "Don't You (Forget About Me)" in his room.
6. And while the high school's name is never explicitly stated, this poster suggests Ferris Bueller goes to the same school as The Breakfast Club kids.
7. It was apparently cool to carry around boomboxes in between class periods at Shermer High.
8. The disguise Ferris wears to pick Sloane up at school is from the mannequin in his room.
9. The nurse who pulls Sloane out of class is named Florence Sparrow, a play on Florence Nightingale, the pioneer of modern nursing.
10. There's an issue with the close-ups in the Sears Tower scene.
11. Also, check out the hats these dudes are wearing.
12. "Danke Schoen" is actually heard four times in the movie.
13. The synchronized dance to "Twist and Shout" borrows Michael Jackson's "Thriller" choreography.
Fun fact: Kenny Ortega choreographed Ferris Bueller, and would later go on to direct Michael Jackson's This Is It.