Genghis (The Next Chapter)

Genghis Frog is one of the Punk Frogs, a group of four frogs that were mutated and trained by Shredder. As Splinter had named his Turtles after his heroes, the Renaissance artists of Italy, Shredder named the Frogs after his heroes - would-be world conquerors and dictators. In Genghis's case, he was named after the warlord Genghis Khan, founder and emperor of the Mongolian Empire. Genghis wielded a battle axe in the animated series.

History
Shredder had convinced the Frogs that the Turtles were evil.

After the Turtles defeated Shredder, Genghis Frog and the other mutants move in with the Turtles.