Brendon Small of Home Movies (1999) fame provides several guest voices. In the jail where the Monarch is being held, he calls an inmate with five arms "Septopus," as he has seven limbs. The Septopus was a sea creature in one of the Home Movies.
This episode reveals Henchman 21's first name (Gary).
When arguing with his brother Jonas Venture Jr., Thaddeus "Rusty" Venture says, "Look Twiki, I have some bitty, bitty, bitty big government contracts I've gotta get cracking on. I'm bitty, bitty back in action and there are bitty bitty bills to play!" This is a reference to and imitation of Twiki, the robot character voiced by Mel Blanc (and Bob Elyea for five episodes) on the television show Buck Rogers in the 25th Century (1979-1981).
In a nod to the original Poltergeist (1982), Dr. Orpheus emerges from "the other side" the same way as did Carol Anne and her mother, i.e., a falling through a portal in the ceiling, covered in a thick layer of pink sludge.