We've all heard of art imitating life, or vice versa. This is a case of fan art that eventually became a reality, although it's a little more complicated than that. The original 'Invincible' character was the work of Robert Kirkman and Cory Walker. Kirkman wrote the stories, and Walker drew the pictures. Eventually, Kirkman left and was replaced by Ryan Ottley, but Kirkman stayed on right through to the end of the series.
Kirkman and Walker remained on good terms, with Walker even returning on occasion for special issues and features. In his spare time, he responded to a fan request to re-interpret his original Invincible design as a woman. 'Invincigirl' was the result of that process, and Kirkman both saw it and liked it. He liked it so much, in fact, that in the very final issue of the comic books, he brought the character in as the daughter of Invincible, leaving things open ended for a possible continuation. How cool is that?