“Stargirl,” the latest heroine born into the CW’s version of the DC comic book universe, harkens back to the classic 1999 comic book series “Stars and S.T.R.I.P.E.” Geoff Johns, the executive producer of the TV adaptation and writer of the original comic book, gathered his inspiration from an even older source, DC’s “Star Spangled Comics” (1941). “Star Spangled Comics” had a unique premise featuring a child hero, with an adult sidekick. Johns took the idea, polished it up and ran with it, merging the influence of the historical DC child-hero with the more tangible inspiration of his own sister, Courtney. An Undying Love Johns’ sister, Courtney, passed away tragically in…