Mr. X was a crimelord who found Mondo Gecko when he started to mutate. Mr. X raised Gecko to be a criminal. The Teenage Mutant Ninja Turtles were involved after Mr. X stole a bomb from the military, blackmailing them for money. In the end, the Turtles convinced Mondo Gecko to change his ways and help our four green heroes defeat Mr. X.
- Mr. X shares many similarities with the same-named main antagonist of the Streets of Rage video game series, including that both are very powerful crime bosses. The first Streets of Rage game was released a month before his debut episode aired. Interestingly enough, Mondo Gecko's clothes are slightly similar to those worn by Skate, a playable character in the second and third Streets of Rage games.