While on his way for a date with Sapphire Stagg, Metamorpho is suddenly interrupted by the Justice League (Superman, Batman, Flash, Green Lantern, and Atom) who have come to select him as the next member of the JLA. This initiation is interrupted by the arrival of the Unimaginable, an alien being that has been watching the JLA and has grown a desire to be part of the team. Metamorpho, declines membership, prompting the Unimaginable to become more aggressive about being allowed membership in the group.

Metamorpho then teams up with the JLA in stopping the Unimaginable, who goes on a rampage to prove his power to the JLA. Working together, and fighting the creature across space, the JLA and Metamorpho manage to destroy the Unnamable. Afterwards, Metamorpho asks Green Lantern to try and change him back to a normal human being, however when GL attempts it with his power ring it fails due to a yellow radiation being one of the elements that makes Metamorpho the super being that he is. After his experience with the JLA, Metamorpho reconsiders the idea of being in a team, however he only accepts a standby membership in the group.

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