Lyle Bolton - Batman: The Animated Series

Formerly a "respected" head of security at Wayne Enterprises, Lyle Bolton was appointed chief of security at Arkham Asylum at the recommendation of Bruce Wayne. 

However, his cruel and abusive treatment of patients led to disciplinary action and dismissal. 

Furious, Bolton vowed revenge—not on the patients, but on those he blamed for Gotham's villainous community: the police, politicians, press, and doctors who failed to permanently eliminate the city's costumed criminals.

After disappearing from public life for six months, Bolton resurfaced as the vigilante "Lock-Up," claiming to be Batman's greatest ally and Gotham’s ultimate jailer. Taking several people hostage, including Mayor Hamilton Hill, Summer Gleeson, and Commissioner Jim Gordon, he intended to execute them.

Defeated by Batman and Robin, Bolton was sent to Arkham Asylum. He happily accepted this, convinced that this was where he belonged—keeping a watchful eye on Arkham’s patients from inside its walls.

Emile Dorian - Batman: The Animated Series

A rogue geneticist and pioneer in DNA splicing, Dr Emile Dorian, developed a fascination with cats. His early experiments caused painful, irreversible mutations, and his creation of the mutagen T-99 further cemented his reputation for animal cruelty. Ostracised by the scientific community, Dorian was forced to leave mainland Gotham and continue his work on a remote island off the coast.

There, he created two human-animal hybrids: Garth, his servant, and Tygrus, whom he regarded as his son and the pinnacle of his research. When Tygrus confessed to feeling lonely, Dorian sought to create the perfect companion for him. Believing cat burglar Selina Kyle to be the ideal match, he sent Garth to kidnap her and transformed her into a human-cat hybrid.

Selina’s abduction drew Batman’s attention. Dorian unleashed Tygrus to hunt the Dark Knight across the island, but when Tygrus discovered that his “father” viewed him merely as a weapon, he turned against Dorian, accidentally setting the lab ablaze. Despite this, Tygrus saved Dorian’s life and handed him over to Batman.

Batman delivered Dorian to the GCPD, and he was later committed to Arkham Asylum.