The Ultra-Mech Unlimiteds were a type of Mech manufactured by the Drek Industries on Quartu. They were designed and mass-produced by the Giant Mech Scientist, who used his enlargement device to transform conventional robots into massive killing machines.
These Mechs were about 30–41m ft tall and all painted yellow. Their main weapons included a spiked ball armed with a hidden rocket launcher, two claws, and an even larger rocket launcher. They were extremely aggressive, as the advertisements recorded a Mech blowing up its creators.
Ratchet and Clank decided that these robots had to be destroyed, and they enlisted the help of the Giant Mech Scientist. He too sought to destroy the monsters he had unwillingly created for Drek. The Scientist used the device to turn Clank into Giant Clank, making Clank an even match for the Ultra-Mechs. Using his new arsenal of weapons and brute strength, Clank destroyed all of the Ultra-Mechs, once again interfering with Drek's plans for galactic domination.