In the first of the diner scenes, the camera moves towards Sam & Dean but along the way, the camera passes by a woman sitting at the counter talking. This woman is played by Jensen Ackle's sister, MacKenzie (the person she is talking to is her real life husband).
Bobby refers to captive Chet as 'Chatty Cathy'. From 1959 to 1965 Chatty Cathy, a pull string talking doll, was second only to Barbie in sales. The doll had maybe a dozen lines it could recite. Pulling on the string powered a vinyl-disc-and-needle phonograph in the doll's torso. In the 1963 The Twilight Zone (1959) episode Living Doll (1963) the voice of the increasingly homicidal 'Talky Tina' was done by the same actress who voiced Chatty Cathy.
When Chet explains how he tracked Sam and Dean, Bobby says, "Great. Just what we need -- a Mensa monster." He is referring to the oldest and largest international organization of persons with high IQ's.
In the opening scene where the two leviathan (posing as Sam and Dean) rob a bank, Jared Padalecki was injured by his automatic gun while spraying bullets in the air.
Due to him being very tall, when he held his gun above his head to do this it was not in frame and so the director asked him to hold the gun at eye level instead of above his head. Unfortunately as this particular gun ejected shells from its top, holding it at this height and aiming upwards caused the casings to hit Jared in the face, narrowly avoiding his eyes and causing bleeding and minor burns. First aid had to be called in and Jared finished the scene with more makeup on to cover the injuries.