The number for Dean on John's answering message was 866-907-3235, which for a time was an operational number with voice recordings by Jensen Ackles. It is no longer in service.
Sam tells Sairie the exact words that his dad told Dean when their mother died.
This is the first episode to explicitly state that Sam has some kind of psychic powers.
The Cymbal-banging monkey is a reference to Stephen King's Short story "The Monkey", first published in 1980 "Gallery Magazine," and later included in the book 'Skeleton Crew" (1985).
While the show uses mainly Canadian actors, Jenny, who lived in Kansas, was played by Kristin Richardson, who was actually born in Kansas.