Baby

Baby is  a parasitic alien life-form from the anime Dragon Ball GT. He was created by combining the DNA of the Tuffle King with a robotic body. He is the first of the three arc villains in Dragon Ball GT and the main antagonist of the Baby Saga.

Baby was created by the surviving Tuffle scientists near the end of the Saiyans' genocidal campaign against them, a conflict instigated by King Vegeta so he could rule the planet and steal the Tuffles' technology. Baby was given the source DNA of their king and was launched into space on a ship with the remnants of the Tuffle king with him before the entire Tuffle race was wiped out. As a result, he possesses an intense hatred for the Saiyans, who killed off the Tuffles and took over their planet (Planet Plant, renamed Planet Vegeta after the Saiyan conquest).

At some unknown point, he created Dr. Myuu, giving him the designs for creating the machine mutants and to resurrect him later on. However, Myuu was programmed to believe that he was the one who programmed Baby and not the other way around.

Goku, Pan and Trunks first encounter Baby in Dr. Myuu's Lab, and Trunks destroys his incubator. However, Baby manages to survive and engages the Saiyans in battle, but is overwhelmed and forced to hide himself inside Myuu's body. Once in space, Baby bursts out of Myuu's body, revealing he was the one who created Myuu before he went over his plans to kill the Saiyans and since they believe him to be dead, he starts planning to catch them off-guard.

Using one of the Black Star Dragon Balls, Baby finds a ship with many passengers aboard and, after killing a majority of them, possesses a young alien boy and lures the Saiyans to the ship. When they arrive, they take him to a medical planet, where he comes up with a plan to steal one of their bodies. Stealing the body of a doctor, he tricks Trunks and tries to possess him, but Goku and Pan show up to save Trunks, with the Saiyans revealing they knew he was alive and wanted to draw him out.

They engage in battle, with Baby managing to enter Trunks' body through a cut on his arm, but Trunks manages to turn Super Saiyan and forces Baby out. However, it turns out Trunks had some of the Tuffle parasite's DNA put into him, and Baby is later snuck off the planet in a space shuttle. Having tasted the power he has been seeking, Baby kills all of the passengers, absorbs their energy and decides to go to Earth in order to obtain more power from the Saiyans there.

Eventually, Baby arrives on Earth, where the few remaining Saiyans reside. Baby is able to infect everyone on the planet except for Mr. Satan, Uub and Good Buu, and takes over several of the Z-Fighters, eventually settling on Vegeta as his permanent host. Goku battles Baby after he returns to the brainwashed Earth, but Baby is able to defeat Goku, even after he goes Super Saiyan 3, due to his child body being unable to maintain that level of power. Baby launches a final attack at Goku, who is teleported away at the last second by Kibito Kai.

Baby believes Goku to be dead, so he uses the Black Star Dragon Balls to wish Planet Plant back into existence. Uub, Goku's student and friend, arrives to avenge his fallen mentor and fuses with Good Buu to become Majuub, but Baby turns Majuub into chocolate and devours him. Goku returns to Earth with his newly-restored tail to fight Baby once more, but despite his new power, he is unable to defeat him. Goku then transforms into a Golden Great Ape and goes on a rampage, overwhelming Baby before Pan manages to get him to regain control of his senses, thus allowing Goku to achieve the power of Super Saiyan 4.

Baby proves to be no match for Super Saiyan 4 Goku, as even his strongest attack only does superficial damage to him. As a last resort, the Tuffleized Bulma brings out a Blutz-Wave Amplifier to help Baby, and as a result of using it, Baby turns into a Golden Great Ape. Goku continues to fight and is eventually able to defeat Golden Great Ape Baby with the help of Gohan, Goten, Trunks (who were freed from Baby's infection), Mr. Satan, Majuub (who had been freed from Baby's body) and Pan.