Appearing in "Deadly Mutant Arkham Inmates"
- Mad Hatter
- Mister Freeze
- Poison Ivy
- The Joker
- The Riddler
- Shredder (Mentioned only)
Synopsis for "Deadly Mutant Arkham Inmates"
On a rooftop, Batman, Leonardo, and Raphael meet with Commissioner Gordon about a breakout at Arkham Asylum. There, they encounter Penguin who reveals that Ra's al Ghul and his League of Assassins have allied with Shredder. While heading back to the rest of the group, Leo collapses due to the mutagen wearing off.
In the Batcave, Robin arrives to find Donatello, Michelangelo, and Casey, and the four have a brief altercation before Batman and Raph arrive with a weakened Leo. Casey explains that due to the mutagen reversion, Leo only has twenty-four hours before his mind shuts down and urges the Turtles to return home immediately using a one-time use dimensional slingshot. After Robin reveals that the League of Assassins is converging upon Gotham, the Turtles and Batman part ways.
When Batman and Robin arrive at Arkham, they are greeted by Penguin, who has been transformed into his namesake, and they discover themselves surrounded by Arkham residents contaminated by the mutagen.
- No special notes.
- No trivia.
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