Also known as 'Earth-A', Earth-721 is home to a Reed Richards that became the rocky Thing and a Ben Grimm that became the stretchy, flammable Mr. Fantastic. It was briefly visited by the Thing of Earth-616, and became involved in a scheme by Arkon to pit three worlds against each other in nuclear wars. Despite the presence of a Thing and a Mr. Fantastic, almost no natives of Earth-721 appeared to have any superpowers.
A scientist from Earth-A created a device that would allow his fellow Earth-721 inhabitants to travel to Earth-616 and transform into their superpowered counterparts, complete with all their powers and paraphernalia. This clandestine replacement of Earth-616's superhumans was discovered due to Jennifer Walters sleeping with the Juggernaut, which Earth-616's native version insisted repeatedly she had never done despite rumors to the contrary. With the plot uncovered, the Reed Richards from both universes quickly set to work, sending both abductors and abductees back to their home universes, before destroying the dimension-crossing device.
- There's an alternate version of Earth-A, Its name is Earth-9532, which was possibly destroyed by Vangaard.
- 30 characters that originate from Earth-721
- 12 appearance(s) of Earth-721
- 1 minor appearance(s) of Earth-721
- 1 mention(s) of Earth-721
- 23 image(s) of Earth-721