The scene in which The Monarch drops his robe to reveal a tattoo on his back resembles a similar moment in Red Dragon (2002).
First appearance of the Order of the Triad (Dr. Orpheus, Jefferson Twilight, and The Alchemist).
First appearance of the Murderous Moppets (Tim-Tom and Kevin).
The scene of Dr. Venture washing the walking eye is a parody of the car washing scene from Cool Hand Luke.