...the car the brothers drive is a 67' Chevrolet Impala...

...that the registration number is KAZ 2Y5...

...and that there are five identical '67 Chevy Impalas being used on the show?

...that Dean's cell phone number is 866-907-3235?

...that Sam and Dean were named by show creator Erik Kripke after two characters from a classic American book called 'On the road' by Jack Kerouac? Kripke always names his characters inspired by other characters, and he named the Winchesters Sam and Dean because the book is about "a big, mythic American road trip" - and the Winchester brothers are doing pretty much the same thing.

...the actors and show creators/writer often check the internet right after the airing of an episode, to find out what the fans think and want to see on the show - and sometimes take this into account?

...Jensen Ackles was considered and auditioned for the lead role of Clark Kent in the hitseries Smallville, about the early years of Superman? Eventually, this role went to Tom Welling - according to Jensen: "I think they made the right choice".

...Jensen and Jared often do their own stunts?

...that in episode 1.06 'Skin', Jensen had a body double for a couple of shots during the scene where he, as the shapeshifter, sheds his skin?