Mondo Gecko

Mondo Gecko was created by Mirage Studio's artist Ryan Brown. In the 1987 TMNT cartoon, Mondo Gecko began his life as a normal lizard who fell into New York City sewers when the TMNT were mutated, and he also became mutated. However, Mondo Gecko was picked up and carried away by an unknown man. One night, Michaelangelo had a bad dream and woke up. When he heard noise up on the streets, he went up and met robbers. Among the robbers were Mondo Gecko, now a mutated and talking lizard who was raised by gangsters. Mondo Gecko was now a member of a gang who worked for "Mr. X", a gangster boss. Michaelangelo convinced Mondo Gecko to turn on Mr. X. Together they fought Mr. X. After this, Mondo Gecko ends his career as a criminal and moves to the sewers and becomes "neighbors" with the TMNT and Splinter.

In the Teenage Mutant Ninja Turtles Adventures comic series published by Archie Comics, Mondo Gecko started his life as a human teenage boy playing in a local metal band who practiced in Shredder's old hideout. One day, Mondo Gecko accidentally got mutagen on him and because his latest contact was with his pet lizard he carried on his shoulders, he mutated into a talking human lizard. His girlfriend, Candy Fine, decided to split up with him. In this version, Mondo Gecko was also a skilled skateboarder. Later, he became a member of the team The Mighty Mutanimals and eventually got back together with his girlfriend Candy. The entire team died in a massacre that made news because it was a surprising occurrence in a version of the Teenage Mutant Ninja Turtles comic supposedly aimed at kids. The story was also surprising because it involved time travel and could easily have undone the deaths but did not. Because these comics were different in style and storyline and came from an alternate publisher, they are not part of the official Turtles canon.