Dean compares himself to Jimmy Stewart when he is in a leg cast
Dean calls Sam "Girl, Interrupted"
The girl "Amy Pond" references the Dr Who companion of the same name who The Doctor met as a child and then due to Tardis / Time traveling hiccups, came back to find her as an adult.
Ad playing on TV is for "My Bloodiest Valentine" - Jensen Ackles was in "My Bloody Valentine."
T-shirt on convenience store clerk; Jensen Ackles voiced the Red Hood in the animated movie