The Ultra-Mech pad was the device that transformed Clank into Giant Clank. It was first seen on Clank's homeworld of Quartu, where a scientist was tricked into creating it in order to produce Drek's Ultra-Mech Unlimiteds. He allowed Clank and Ratchet to use it to destroy the Mechs and then programmed all existing machines to enlarge only Clank. They were used again in later games.
In Secret Agent Clank, Qwark claimed to have used a "growth pad" that he modified to become giant and fight the Giant Robot Lizard.