A question for those who have an opinion. When is it considered a rip-off of another work? How big of a percentage is over the line? Many stories are "similar" to another theme or plot but are unique in their own way. Is this decision made by attorneys and pay-offs, or is there an invisible line? Apparently somewhat similar concepts... Alien take-over of bodies: Invasion of the body snatchers Puppet Masters Impostor The Hidden The Thing (feel free to add more) Replacement (look alike/similar) Robots Screamers Terminator Blade Runner Battlestar Galactia I'm confused as to what is new and what is "actionable" plagiarism ?? Can someone explain?