April O'Neil was a close ally of the Turtles, and they even lived with her in her apartment for a couple of years. She was a computer programer, and originally introduced as an assitant for Baxter Stockman. When her emplyment with Stockman ...ended, she reopened the Second Time Around antique store she had inherited from her father. April dated Casey Jones, off and on, for years, and eventually moved in with him and his daughter, Sahdow. She raised Shadow as her own daughter, and they were as normal as a family could be with the Turtles around.
April was not born, biologically, like most people, but was instead drawn into existance by her father with a magic crystal. Her mother could not have any more children after she gave birth to their first child, Robyn, but desperately wanted more. Her father, being a very skilled artist was able to draw a realiztic baby with this magic device. That baby grew up to be April.