Earth-12

This universe is very similar to Earth-616, except that the Calvin Rankin (also known as Mimic) on this Earth joined the Brotherhood of Evil Mutants and fought against the X-Men. After the battle the Brotherhood left Calvin to rot in jail, however Professor X saw amazing potential in the young man and offered him a place at his Institute. Calvin agreed and joined the X-Men, eventually becoming one of its most honored members and even a leader of the team.