Earth-751263 or better known as the Counter-Earth is actually an Earth-like planet from the other side of the sun. This planet had Humans that evolved from a wild Jurassic world and was ruled by Dinosaurs. 50 years before John Jameson and Spider-Man landed on the planet, a man from Earth arrived because he was angry with the human race for causing wars on Earth.
The man married with a woman from the planet and raised a family, but one day he noticed that the behavior that he left behind started showing up on Counter-Earth. To keep this planet a paradise, he started to experiment on animals in an attempt to create a peaceful race. Once he succeeded, he named the race "Beastials." The Beastials eventually decided to take over the planet and to control the human citizens of Counter-Earth.
About thirty years later, the man built Castle Wundagore and gave himself the name "the High Evolutionary".
Twenty years after that, John Jameson decided to investigate the planet after NASA's Alita 1 was destroyed by the High Evolutionary in an effort to keep his planet unknown to the people of Earth.
Unbeknown to Jameson, he inadvertently brought Venom and Carnage to the planet. Their plan was to conquer it and begin a new symbiote planet. Because of them, Jameson was stuck on the planet for six months before Spider-Man was able to make it there to help him. Unfortunately, Spider-Man's shuttle was destroyed during the landing as well. Unable to leave, he decided to join Jameson and his Human Rebels to destroy the High Evolutionary.
This planet has a robotic police force called the Machine Men, each Machine Man is a "law and order" creature that was programmed by the local Knights of Wundagore, the Beastial elite unit of the High Evolutionary.
- On the Counter-Earth: Some parallel versions of Spider-Man's friends and foes:
- The Machine Man, who is based on X-51.
- The Green Goblin who is one of Spider-Man's friends and a Human rights activist.
- Reed Richards who is rich and mutated into a Hulk like-monster. He is friendly with the Beastials.
- Gwen Stacy that lives in a secret village called "Harmony" near New York City, where Humans and Beastials live together in peace.
- The Chameleon of Counter-Earth is a lizard Beastial that murdered Humans for their sub-skin ID Chips.
- Earth-751263 is the Universe where the comic book based on the Spider-Man: Unlimited animated series released in 1999 takes place.
- About 70% of the Counter-Earth is covered with water, and 97% of that is saltwater oceans.