The Zookeeper is Samuel Register, a brilliant geneticist turned super-villain and an enemy to Beast Boy. Register worked with Beast Boy's parents Mark and Marie Logan, eventually becoming obsessed with their son's transformation. He accidentally infected himself with a different version of the same virus that created Beast Boy, Sakutia, giving him the ability to transform into different animals. The Zookeeper was created by Geoff Johns and Tom Grummett, first appearing in Teen Titans (Volume 3) #13. (2004)

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