Daughter of Chris Kelly and Arlene (Arliss) Kelly, Christine Kelly was born like a perfectly normal little girl. After her parents divorce, Christie lived mostly with her mother and spend less time with her father. As she grew she became closer to him and even visited him in his Rocky Mountains Retreat. During one of her visits, Ultiman was making one of the meteor power recharge. But that time something went wrong and the meteor exploded. As effect, Christy received all the powers of Ultiman, meanwhile her father was apparentely destroyed.

Chris then continued her father's crusade using the name of Ultragirl.

Same as the other characters of Big Bang Comics, Ultragirl is a homage character, in this case, Supergirl's.