A little girl Named Katie Burke was battling cancer for three years, Joker has given the billionaire his happy pills that made him laugh then choke to death. The Seagate Amusement Park was an inspiration by Katie's drawings.
Batgirl teams up with Robin to save Gordon from Joker and Harley Quinn in the Seagate Amusement Park.
- Barbara Gordon/Batgirl
- James Gordon
- Gotham City Police Department
- The Joker
- Harley Quinn
- Joker's Henchmen
- Edward Burke (Voice Only)
- Dr. Penelope Young (referenced only)
- Batman/Bruce Wayne (reference only)
- Penguin (mentioned only)
- Starro (Cameo)
Seagate Amusement Park
Used to be a Sartorico oil rig, but was transformed into an offshore amusement park that contained a large Ferris Wheel among other rides. The island could be seen from Gotham City during the Arkham Knight Incident.
- Harley Quinn sported her trademark black and red ensemble outfit from Batman: The Animated Series.
- At one point, Joker refered to Batgirl as "Bat-fake", the same insult he would refer to Terry McGinnis in Batman Beyond: Return of the Joker. Coincidentally, both characters also effectively replaced Batman at those times (although Batgirl's case was more temporary than permanent).
- Joker once again used the alias of "Jack White" to manipulate someone.
- Penelope Young was referenced in an audio file.
- The Laughing Fish made a startling cameo in the game. An animatronic of a jokerized fish appeared and frightened Batgirl as she explored the Ghost Ship.
- Starro made a cameo in a secret room between the Ferris Wheel and the Great White. In addition, a billboard featured an advertisement for the Starfish Freak, which alluded to Starro's ability to take over people's minds via spores.
- The name of the character, Edward Burke, who built the Seagate Amusement Park, might be a reference to the DC Comic book super-villain called Planet Master.
- Near the Great White, there was a large floating balloon of a clown with a long nose, which alluded to one of the Joker's float balloons from the 1989 Batman film by Tim Burton.
- Some of Joker's thugs, when preparing to "feed" a GCPD officer to the Kraken, commented about how they could probably revive the Kraken by extracting DNA from "orange glass" (with the GCPD correcting them by stating that it's amber and that it's actually hardened plant sap rather than glass), which alluded to the basic premise of the Jurassic Park franchise.
- Dual play was featured for characters Batgirl & Robin as well as Joker and Harley Quinn. Hackable objects can be interacted with more ways than one, such as first luring henchmen to a machine before blowing it up, knocking out the enemies.