This isn't the first time Neal Patrick Harris has been a singing super villain. He was also Dr. Horrible in Dr. Horrible's Sing Along Blog.
The Music Meister later made his live-action debut in the second season of Supergirl (2015), and also crossed over onto The Flash (2014); played by Darren Criss, the crossover reunited him with fellow Glee (2009) alumni Melissa Benoist and Grant Gustin.
This is the first episode to not feature a teaser sequence, which usually features the end of one adventure before Batman embarks on the main plotline.
The Music Meister wears a total of 11 outfits.
In the DC Comics universe, Green Arrow and Black Canary married each other.