Dr. Milo first appeared in "Cat Scratch Fever", and was voiced by Treat Williams. Milo engineered a plague to infect Gotham City's stray pet population for Roland Daggett. That plague also affected Catwoman when her cat, Isis, attacked her. When Batman stumbled onto that plot to look for the antidote, Milo unleashed an infected dog who attacked Batman and Batman got away with the antidote and used some of it on the dog during mid-chase. Milo was later seen about to drive a truck that would distribute the antidotes. Daggett told Milo that he better make sure that dog got away with Batman because if Batman evaded it, Daggett instructed Milo to keep driving as far away from Gotham in the truck that he's in would take him. Milo later reappeared in "Moon of the Wolf" where he was the one who was responsible for making an untraceable steroid/wolf hormone (when he got the Alaskan Timber Wolves from Zookeeper John Hamner) derivative for an athlete named Anthony Romulus, which not only enhanced his athletic abilities, but also turned him into a living werewolf. When Romulus turned into a werewolf in the climax, Milo then realized too late that he had unleashed a monster that he could not control. Milo (who was really a coward at heart) screamed at Romulus that he would give him whatever he wanted, but Romulus lost his human reasoning during the transformation and beat up Milo mercilessly like the animal he was transformed into, and Milo was knocked out by Anthony. Milo was later seen loaded into an ambulance. When Milo stated that they couldn't convict him of anything, Commissioner James Gordon quoted: "Don't bet on it."
Milo later resurfaced in Justice League Unlimited, and was voiced by Armin Shimerman. He was seen as a member of Project Cadmus. Amanda Waller demoted Milo to a lower position after a failed warthog experiment in his research of Dr. Kirk Langstrom, the former Man-Bat. He then entered a room where Cadmus held Doomsday. After explained his creation and his fight with Superman, Milo set Doomsday free to take revenge on Waller. When Waller found out that Milo had released Doomsday and vowed to "kill Milo," a guard told her that Doomsday had beat her to it.