9. Challengers Of The Fantastic
Arguably one of the greatest crossovers in human history occurred when DC and Marvel Comics banded together and created a short-lived line of crossover comics where the characters of each universe literally crossed over, and became new beings, in what is referred to as the Amalgam Universe.
This universe was full of interesting and often strange character combinations such as Batman and Wolverine fusing into the hero known as Dark Claw. This unexpected brand fusion also affected Marvel's first family, who were fused with Challengers of the Unknown, a team that inspired the Fantastic Four.
Ironically the Challengers of the Unknown were created by Marvel legend Jack Kirby, who also created the FF, meaning both of his creations got the chance to work together as a whole new team of super-strong, super-strange heroes.
With new identities, a new mountain home base, and all sorts of weird new superpowers (like the Thing growing four arms and becoming a senator), the Challengers of the Fantastic are a version of the Fantastic Four that should never be forgotten.