Aqua's hair decoration is made of two small yellow spheres attached to a larger blue one - a model of a water molecule, an apt design for a water goddess.
Darkness's ineffectual swordsmanship is based on the Darkness attack in the "Final Fantasy" video games, which causes a character's physical attacks suffer a drop in accuracy.
Strangely, Yunyun appears in the Season 1 Opening, despite debuting in Season 2.
Erica Mendez, Cristina Valenzuela, Erika Halarcher all worked together on Hunter X Hunter 2011