When Dean calls up the cell company to track Sam's phone, he uses the name Wedge Antilles. This is the name of a Rogue Squadron fighter in Star Wars. Wedge Antilles (portrayed by Denis Lawson) is the only non-main character to appear in all three original Star Wars films - and survive.
The second consecutive season of 3 which used an AC/DC song to accompany the opening recap. The third season used Hell's Bells, this season used You Shook Me All Night Long, and Season 5 uses Thunderstruck.
Castiel dresses like john Constantine in DC's vertigo line
Dean crawling out of his coffin and across the street to the gas station as well as chugging water was reminiscent of Beatrix Kiddos rise from her grave in Kill Bill: Vol. 2 (2004).