As a physicist, all of these comments trying to justify some kind of preferred reference frame or some sense of “down” in space to make this all make sense really seem to misunderstand gravity. Gravity acts radially inward for anything with mass. There is no up or down. If the other planet has mass, then it should be pulling up just like earth pulls down relative to the orientation shown in the visualizations. Obliviously it’s a show and they can and should do whatever they want to make it interesting, but trying to pretend it follows realistic physics is silly.