The concept of a "Counter-Earth" sharing the same orbit as Earth has long been a staple of sci-fi. Just two examples are the Gerry Anderson production "Journey to the Far Side of the Sun" (1969) aka "Doppelgänger", and the entire notorious long-running "Gor" series of books and films. - Trojan Planet Suspected of Sharing the Same Orbit as Its Sibling - https://gizmodo.com/trojan-planet-suspected-sharing-same-orbit-sibling-1850660567