During the 1970s there were several crossovers between the Marvel and DC Universes, and not just between the Avengers and the Justice League. While on Earth-One, the mightiest heroes of Earth-X the Freedom Fighters... who had originated on Earth-Two... faced the Crusaders. Themselves artifically spawned from the machinations of the evil Silver Ghost who followed his foes from Earth-X, these five Crusaders mimiced the Invaders over on Earth-616. With a shield-wielding warrior and his sidekick, a dweller of the deep and a pair of hotheads, both teams were legends of World War II... only the Crusaders were fictional characters whereas the Invaders were real on their world.
And while those faux-fighters on Earth-One were merely comicbook fanboys employed by the Ghost, on Earth-616 the counterparts of the Freedom Fighters were folks from England enlisted and empowered by a Nazi agent to be plants for the German cause. Consisting of Captain Wings, Dyna-Mite, Ghost Girl, the Spirit of '76, Thunder Fist, and Tommy Lightning... these Crusaders were mirror-images of the Freedom Fighter's Black Condor, Doll Man, Phantom Lady, Uncle Sam, Human Bomb and the Ray. While the Invader-clone Crusaders of Earth-One were one-and-done dupes for the ex-Nazi Silver Ghost, the Fighters-clone Crusaders endured for a time on Earth-616 before going their separate ways. Nevertheless, this was yet another instance of twin realities echoing the other.