Three teenage bad seeds - Gizmo, Jinx and Mammoth - were about to graduate from the H.I.V.E. Academy and were looking to be employed by criminal patron Slade. But first he asked them to pass one final exam: destroy the Teen Titans. Gizmo, covered head to toe in high-tech gadgets, is a pint-sized boy-genius with a bad attitude. Mammoth is not just big for his age, this ultimate bully is big for his species. Jinx is a beautiful but arrogant witch able to cast hexes that bring her enemies the worst kind of bad luck.
The three criminals took over Titans Tower - but were ultimately defeated by the Titans. They are still trying to graduate the H.I.V.E. Academy to become villains in their own right.
Gizmo often clashes with Cyborg - who provides a challenge and a threat to the diminutive high-tech genius. Gizmo also allies himself with the "H.I.V.E. Five" - a mischievous group of fellow H.I.V.E. Academy students. So far, their collective efforts have met with little success.
In Winner Take All, Gizmo battles Cyborg in a competition to see who takes all and is the champion of games. This is the only time he uses his goggles in the whole Teen Titans series. He uses his flight wings, machine guns, and spider legs to attempt to beat Cyborg. In the end, Cyborg ends up beating Gizmo by destroying his Spider Legs.
He is voiced by Lauren Tom (he was voiced by Tara Strong in "Revved Up" and in "Titans Together"). Gizmo was redesigned into a probably pre-teen kid (as opposed to being a middle-aged dwarf as he was in his comic book form). He works with Jinx and Mammoth most of the time, although in the episodes "Car Trouble", "Revved Up", "Crash", and "Winner Take All", he is seen conducting solo acts.
Gizmo's main gadget is a harness that can deploy wings, large mechanical spider legs, a device that creates holographic copies of himself, and a technological suit of armor. His knowledge of computers and incredible hacking skills make him a formidable foe for the Titans (though constructing a Level 4 Containment Field is hard, even for him). He also has a short temper and swears in pseudo profanity ("crud" and "snot" are his most frequently used terms). He has a special enmity with Cyborg and was able to tell that something was wrong with him when Cyborg went undercover as "Stone" at the H.I.V.E Academy. He later forms The H.I.V.E. Five with Jinx, Mammoth, See-More, and Private H.I.V.E. He was sent with Billy Numerous to capture Kole and Gnarrk, but failed when Kole turned into a boomerang and severed his spider legs.
During the final battle of "Titans Together", he was knocked unconscious by a giant hex from the reformed Jinx while trying to escape. Kid Flash placed him in the Brotherhood of Evil's freezing machine, taking him out for the rest of the battle.
Gizmo is the only villain to appear in all five seasons of Teen Titans (as opposed to Slade, who is seen only once in the third season as an illusion and as a Slade-bot in the last season).
Gizmo has also made several appearances in Teen Titans Go!. He is the main villain in issue #9.