The song playing when Dean goes to the bar is "Worlds Collide" by Louden Swain, real life band of Rob Benedict, the actor who plays Chuck.
The episode title is a play on the late '90s group The Spice Girls.
Professor Morrison is played by Harry Groener, who played Season 3 Big Bad, Mayor Richard Wilkins III in the Buffy the Vampire Slayer series. This makes him the latest Slayerverse alumni to appear on the show, following the likes of Jeffrey Dean Morgan, Amy Acker, Julie Benz, Amber Benson, Mercedes McNab, Aldis Hodge, Chad Lindberg, Brittany Ishibashi, Charisma Carpenter, James Marsters, and many more.
This episode takes place in Seattle, and features Amazons. Ironically, Seattle is the headquarters of corporate giant Amazon.