Inspired by…: The idea of the Earth being occupied by a hostile alien force is based on occupation by Axis Forces in Europe and Asia in World War II and the occupation of Iraq and Afghanistan by American-led coalition forces.
Separated-at-Birth Casting: Nobody else in the extended Bowman/Kenner clan look particularly close, but Sarah Wayne Callies (Katie) and Amanda Righetti (Maddie) really could pass for sisters in real life with ease.