I found this list at Huffington Post . Did you know the only high schooler in the movie was the actress who played Sloane? The actor who played Cameron was 29!!
Here are the main points, but if you want to know details read the full article HERE.
1. June, 5, 1985 was probably Ferris' real day off.
2. Mr. and Mrs. Bueller fell in love on set and married shortly after.
3. Though they played brother and sister in the movie, Matthew Broderick was actually engaged to his on-screen sister, Jennifer Grey.
4. Mia Sara, who played Ferris' girlfriend Sloane, was the only teenager playing a high schooler at the time of filming. The actor who played Cameron was 29!
5. Painter George Seurat's famous work, "A Sunday on La Grande Jatte," is the piece of art Cameron is taken with at the Art Institute.
6. (Whew!) Cameron's dad's Ferrari was actually a fake. They destroyed a replica.
7. Charlie Sheen really wasn't on drugs during filming. He did have issue with insomnia and stayed up for a long period of time before filming his scene.
8. Though the film took place in the Chicagoland area, the Bueller home is really in Long Beach.
9. Every license plate in the movie has a meaning. For example, Cameron's dad's car had the license plate "NRVOUS."