Some TMNT stuff really isn't for little kids.
Shadow Jones (also known in the Image continuity as Maria Isabella Puzorelli) is the adopted daughter of Casey Jones and April O'Neil and an adopted niece and friend of the Turtles as well as the adopted granddaughter of Splinter.
Shadow is the daughter of Gabrielle, a waitress at Goathead, Colorado cafe "Graham's Goodtime Grill". Gabrielle would soon meet Casey Jones at her cafe. As Casey one day on one of his strolls accidentally killed a young purse snatcher, he set out on a self-discovery trip. During his journey, he came to Goat Head, Colorado, and met in "Graham's Good Time Grill" the waitress Gabrielle, who took him into her trailer home after Casey was robbed of his car and possessions. At some point soon after, Casey and Gabrielle (whom Casey called Gabe) began an intimate relationship, and later Casey discovered that Gabrielle was pregnant. But the pregnancy was already four months along, and Casey wasn't the father. Though she expected him to leave her, Casey surprised her by staying. Over time, their relationship advanced and soon they were married, and planned a life together as a family. But this bliss was cut short when Gabrielle tragically died in childbirth. (TMNT Vol 1, #58).
With no other family, Casey became Shadow’s legal guardian. Before returning to his mother in New York, Casey scattered Gabe's ashes over a cliff. After reuniting with his mother, he saw April O’Neil (who would quickly become Shadow’s adoptive mother). Shadow grew happily in a large family, which included not only Casey and April, but the Turtles (her adoptive uncles) and their mentor Splinter (her adoptive grandfather). Developing a particularly close relationship with Michelangelo and Raphael, who were living with them in the apartment complex at that time, Shadow became fond of video games (TMNT Vol. 2, #13). She once told April she wanted a baby brother.
After an episode in which she and her family, among others, dealt with Lilith and werewolves ("Darkness Weaves"), April and Casey sent her to Northampton, where she lived under the care of Splinter and Stainless Steel Steve.
As a grown teenager, Shadow started a relationship with a boy from the area, Jay. Since she kept certain details of her life from him, Jay followed her one day secretly back to the Jones Farm, where he was caught by Metal Head and learned of the existence of Splinter and the Turtles (TMNT Vol.4 # 6-7). Later, however, Shadow had learned to her horror that Jay had joined the corps of a radical xenophobic group called Xihad that was rigorously and ruthlessly against extraterrestrial influence on earth, introduced by the Utroms ( TMNT Vol.4 # 24).
In a post-apocalyptic, possibly alternative future Shadow studied martial arts as an adult, was a fully trained ninja warrior, and when looking for her missing sensei, successfully took down the Foot Elite (Tales of TMNT # 69)
Additional details for Shadow's story were written for the Image continuity. Like the rest of the Image continuity, it was expanded from existing Mirage continuity, but these details were disregarded by future Mirage canon.
Soon, however, Shadow encountered ghosts from her past: Her biological father was Albert Puzorelli, a mafioso who had died shortly after he had left her mother. His father, Antoine Puzorelli, learned of Shadows existence and hired the Foot Clan to abduct her for him.
One night when being baby-sat by Michaelangelo, Shadow heard a knock on the door and answered it. Captured by the Foot Clan, she was taken to her paternal grandfather, Antoine Puzorelli. When Raphael learned of Shadow’s abduction he sough council with the Foot, confirming their involvement. He then agreed to kill Antoine Puzorelli for them in exchange for Shadow, a mission he couldn’t complete. Michaelangelo stepped in, disguising himself as a priest in the cathedral where Shadow was to be baptised by Antoine under his family name. Only moments after being baptised (making Antoine her godfather), Michaelangelo dropped his disguise and rescued her, taking her to the top of the cathedral and using his shell to make himself appear as part of the gargoyles statues. Shadow was then returned to Casey and April (TMNT Vol. 3, #6 - 8).
Antoine Puzorelli then had his thugs put his apartment on surveillance in an attempt to locate Shadow. When April caught on to this and told Casey, Casey, April, and Shadow went into hiding in the Turtles’ current hideout in the mausoleum of Westwood Cemetery. While Shadow watched, Casey accidentally clubbed Raphael when he returned to the hideout, thinking him an intruder. Shadow, Casey, and April met back up with Leonardo and Michaelangelo when they brought Donatello to their mausoleum hideout, where he was then revived (TMNT Vol. 3, #11, 12 & 15). When Leonardo chooses to give up his artificial, removable hand, Shadow asks if she can keep it. Leonardo gives her permission (TMNT Vol. 3, #23).
As she grew older, Shadow were taught the basics of self-defense, in which she proved to be a very gifted student. For various reasons, the Turtles have, however, up to now decided not to teach her all the secrets of Ninjutsu. Often Shadow does well in heavy fighting because of own talents and intelligence as well as the help from her "uncles"