Koi has the rare ability to walk on his back legs in balance and sync. He also fights with a scavenger claw made of a rib bone. He is slow on land, weighed down by his enormous muscles, but he is fast in the water, and his huge wings can carry him swiftly through the skies. He is not easily convinced, but Stretch easily pried out the truth from him - that he himself killed Gemira. Not paying attention to the reasoning that he was under mind-control when he murdered her, Stretch and Koi went to a claw battle - to the death. Neither won, since they were evenly matched, but Koi escaped to the future, and was never seen again. He was brought back to the present by Dyamond, but the portal closed and Dyamond was stuck in the present.
Koi is crazy. He thinks that he is awesome after Flame enslaves him, but Flame encourages him that he is a nerd and Koi goes insane. Soon Koi kills Flame by accident, so he is released.