To lure Mary into a trap, Sam says "Bloody Mary" in front of a mirror three times and Mary appears: it's revealed that before Jessica's death, Sam had been having dreams of her being killed in the exact same way as his mother, and that he feels guilty for ignoring what he now thinks were prophetic visions.

This change also makes viewers think differently about everything we know of John, as it is said in Supernatural that John didn't learn about demons and monsters and begin his life as a hunter until after Mary is killed by Azazel.