The ToonTown Penitentiary is ToonTown's biggest jail where the most dangerous villains are kept in.
Current inmates
- Le Quack
- Tetti-Tatti
- Nefir Hasenuf
- Ursula
- Butch and Cassidy from Team Rocket
- Scarecrow
- Bane
- Killer Croc
- Mr. Freeze
- Baby Doll
- Poison Ivy
- Joker
- Harley Quinn
- The Riddler
- Alpha and Omega (The Chaos Twins) (Escaped thanks to Set)
- Honest John and Gideon
- Cleo Quinzel
- Fang
- Magpie