Debuting in the "City At War" storyline Shadow is the daughter of a women named Gabrielle who met Casey Jones at a Goathead, Colorado
cafe "Graham's Goodtime Grill". Nursing the an injured Jones after he was attacked and had his car stolen. The two lived together in her trailer when Gabrielle revealed she was pregnant with a former lover's child.
Gabrielle expected Casey to leave her but surprisingly he stayed. Overtime their relationship blossomed into love and soon were married. But the joy was short lived as Gabrielle or Gabby (called by Casey) died giving birth to Shadow. With no other family, Casey became Shadow’s legal guardian.
City at War
After scattering Gabrielle's ashes over a cliff Casey returned to New York to raise Shadow with the aid of his mother. In a twist of fate Mrs Jones was selling her apartment building to April O'Neil, the two old friends were joyfully reunited.
Returning for a short time to the Northampton Farmhouse they were had an another surprise reunion with the Teenage Mutant Ninja Turtles who instantly bonded with Shadow. The baby was especially close to Michaelangelo who she nicknamed "Rooish". The entire gang sans Donatello and Splinter left to live together in New York.
In the series published by Image Comics Shadow is living in the apartment complex with Casey and April who are romantically involved and raising Shadow together.
While April and Casey are out to celebrate Casey's promotion Michaelangelo is babysitting Shadow. The turtle falls alseep repeatedly re-reading the sane bed time story allowing Shadow to sneak back to playing video games. Hearing someone at the door she thinks her parents have returned but ends up being dragged away.
It turns out the Foot Clan have kidnapped Shadow, they did so ignorant that she was a member of the turtle's extended family as this would violate the truce between them and the turtles. To help make amends they charge Raphael with the assassination of the Antoine Puzorelli the current leader of the New York mob claiming his death would solve both their problems. Deciding to not kill Puzorelli Raphael learned that it was he who had Shadow.
It was revealed that Shadow's biological father was Alberto Puzorelli (Antoine's son) who died sometime after dumping Gabrielle. Taking Shadow to be baptized in St Paul's Cathedral when an acolyte set fire to the priests robe, taking advantage of the distraction the acolyte revealed himself to be Michaelangelo who grabbed Shadow and tried to escape. Unable to evade Puzorelli's men he used his shell to disguise himself as one of he gargoyle statues. Shadow was then returned to her adoptive parents unharmed.