Doctor Harleen Quinzel has lived in Gotham City her whole life. The only child of parents who didn't give much affection, she made every earnest effort in her youth to move with the 'in' crowd at elementary and secondary school and make friends. However, she never quite managed to fit in any of the cliques at high school, and began to channel her energies into gymnastics, which she had been practicing since she was five.
By the time she had graduated from high school, Harleen's gymnastic abilities were of Olympic class and she was subsequently offered a sports scholarship to Gotham University, which she happily accepted. This did not satisfy her though, and she switched her degree to criminal psychology. While enthused and knowledgeable about this field of study, Harleen had difficulty grasping some of the more complex aspects of the subject, and resorted to sleeping with her professor in order to receive an A on one of her final essays. After completing her degree, she remained at university to earn her PhD and graduate with honours. After a brief spell as a counsellor at Gotham Prison, Harleen interned at Arkham Asylum, eventually accepting an offer to become a full time psychoanalyst there.
Spending so much time among these criminals has perhaps given Harleen more food for thought than she would like to admit. Still affected by her loveless childhood, she desires to feel needed, which is perhaps why she works so incredibly well with Arkham patients.
^~*~^ Obviously, Harley Quinn ain't mine. She belongs to DC Comics and the WB. I'm just playing her for fun. Don't sue!