J. Allen Carter was an alien duplicate who served the Imperium and was an antagonist in the Justice League series.
Carter was an astronaut sent by NASA to survey Mars along with another astronaut. While surveying the planet Carter accidently released the Imperium from their prison and was killed by one of the aliens who impersonated Carter using the shape-shifting powers they absorbed from the Martians. The astronaut went back to Earth with the alien duplicate not knowing about his nature.
Two years later, Carter became a Senator of the United States. Using his position, Carter made a proposal to disarm all of the nuclear weapons to the World Assembly with Superman's help. Most of the members agreed with the proposal but General Wells and other military soldiers protested that those weapons would defend the world from aggression. Carter secretly planned to disarm the nuclear warheads to help the Imperium conquer Earth. When Imperium attacked Earth, Carter assured the people of Earth that they could fight back and maintained his disguise while doing so. The Imperium captured six out of the seven heroes who would later become the Justice League and took them as captives. Carter appeared to Superman and the other five heroes and revealed his true nature to them. He introduced the heroes to his leader and told the Justice League that he knows alot about the Earth and its defenses by using his disguise. Batman appeared and sabotaged the power generators of the ship, Carter's skin began to burn from the sun rays as he fought the heroes. He tries to get on the mothership with the Imperium leader but the leader left Carter to be perished.
- Carter's name might be a reference to the titular character John Carter of Mars.