Created by Geoff Johns
| ZOOKEEPER [Doctor Samuel Register]|
Real Name: Doctor Samuel Register
Known Relatives: None
Group Affiliation: former S.T.A.R. Labs employee
First Appearance: Teen Titans Vol. 3 #13 (September 2004)
Doctor Register is a pathologist specialising in unusual diseases. He worked with Mark and Marie Logan when they cured their son Garfield of Sakutia, using a treatment which transformed his physiology, leading him to grow up as the hero known variously as Beast Boy and Changeling. Doctor Register than had a brilliant, if scandalous, career, losing various prestigious jobs due to the extreme methods he employed. Later, he infected himself with Sakutia while working for the San Francisco branch of S.T.A.R. Labs and, after spreading the deadly disease to a host of schoolchildren, he tried to use Garfield Logan for a cure – but only for himself and his career. With similar abilities to Beast Boy – able to transform himself into a variety of creatures, all purple, and use their various talents and abilities, he battled the Teen Titans, finally defeated by Beast Boy himself, who was able to use his own blood to help cure the many infected children. Zookeeper is currently imprisoned in the new Alcatraz. Like Beast Boy, he is seemingly immune to the disease and will keep his powers for life.