1. Supernatural was originally going to be called Unnatural.
2. Jared Padalecki and Jensen Ackles were voted People Magazine's "Sexiest Ghostbusters" in 2005.
3. Jensen Ackles planned to study Sports Medicine and become a physical therapist before moving to LA to become an actor.
4. Dean has killed the most main antagonists on the show.
5. Padalecki's dogs Harley and Sadie share his trailer with him on set
6. The license plate on the Impala is KAZ2Y5
7. The brothers come from the bloodline of Cain and Abel.
8. Dean has entered the most number of realms.
9. Jensen Ackles starred in a TV Movie called Blonde, where his best friend's name was Cass.
10. Jim Beaver’s character (Bobby) was only supposed to make a one-time appearance.
11. Dean Winchester is allergic to cats.
12. The Latin inscription on the barrel of the Colt says ‘non timebo mala’.
13. Sam always wins at Rock, Paper, Scissors against his brother.
14.The original concept for the show had a reporter going to investigate the urban legends and writing about them in his column.
15. The deleted scene of Dean lip syncing "Eye of the Tiger" was ad libbed by Jensen Ackles.
16. For a short period, you could call Dean's phone (866-907-3235)
17. The only known sources of income for the Winchesters are credit card scams, poker games and playing pool.
18.According to set director George Nevman, the set for Bobby's place had around 5000-6000 books.
19. Season 1 had a budget of just $20,000. This includes actor wages and the special effects budget.
20. The series has also developed an expanded universe.

(source from imgur)