Dr. Holiday (voiced by Grey DeLisle) - A scientist for Providence. She is usually seen wearing a lab coat, an orange top, and knee-high boots. She is depicted as the polar opposite of Agent Six, as she is much more in-tune with her emotions, in contrast to Agent Six's stoic nature. She is the only one who sees Rex as more than a machine. Rex sees her as a romantic interest, frequently flirting with her and asking if he can take her to "dinner", but she is more of a big sister in attitude. She repeatedly tries to convince Six to try to relate to Rex, as she understands what he goes through with his amnesia and the pressure put on him by Providence. In the episode "Lockdown", it is revealed that her sister is an incurable spider-like Evo kept in containment at Providence. It is implied that she is being used as blackmail material to get Dr. Holiday to work for Providence as she was involved in a deal involving her life.