Man-Bat in Batman: The Animated Series

Scientist Kirk Langstrom worked as a zoologist at the Gotham City Zoo, experimenting with bat mutagen to create a serum to replicate the creatures' long life. After testing the serum himself, he became the vicious Man-Bat. Though Batman eventually cured him, Langstrom's obsession with the power of the Man-Bat compelled him to take the serum again, and again.