Cowboy BeBop at His Computer: There's an awful lot of reviewers out there that believe the 'Sisters' portion of the title means that cute and punk Giana are sisters rather than being the same person.
Vaporware: The fourth main game, dubbed Giana Sisters 3D, is on hold. It began development circa 2015-2016 but was put on the backburner.
Giana Sisters: Dream Runners
Keep Circulating the Tapes: Giana Sisters: Dream Runners Storybook was an online companion piece that contained the plot of Giana Sisters: Dream Runners. It was posted on Black Forest Games' blog but was removed during a site redesign.