While it was originally stated by Andrew Kreisberg that King Shark having his own episode would be expensive and difficult to pull off, the Flash producers managed to pull through and do it anyway.
Cisco says he can keep a secret, but multiple times he has said that the Flash was Barry Allen.
The Shay Lamden of Earth-1 died on December 14, 2013.
King Shark was voiced by actor and screenwriter David Hayter, famous for providing the voices of the characters Solid Snake and Big Boss in the Metal Gear video game series.
References to "how Felicity is doing" and the A.R.G.U.S. organization requires viewing of the Arrow TV series to fully understand portions of this episode that are not integral to the story.