Upgrade is a Galvanic Mechomorph (a portmanteau of mecho- meaning machine and -morph meaning shape), a mechanical liquid body composed of nanotechnology and able to change shape. The Galvanic Mechamorphs were created by the Galvans and based from Galvan Prime's moon, Galvan B. Originally an uninhabited plantoid, Azmuth and the other Galvan scientists conducted an experiment to make Galavan B inhabitable with self-replicating nanotechnology. However, it caused a unforeseen event when the nanotechnology bonded with Galvan B's minerals and created the first Galvanic Mechomorphs who were recognized as sentient beings and flourished into a civilization. Other than firing positronic plasma beams from its eye, a Galvanic Mechamorph's primary ability is to merge with technology, regardless of size, upgrading it far beyond its original design. While that can control machines in that fashion, Galvanic Mechomorphs are incapable of properly controlling sentient robots. Galvanic Mechomorphs are also vulnerable against electricity and any sort of metal corrosive can compromise their delicate internal workings.
First becoming Upgrade to stop some criminals who were robbing an ATM in "Permanent Retirement", Ben's voice remained the same though sounding more computerized. This is due to Galvanic Mechomorphs being unable to bond with living organisms, thus Ben's transformation into Upgrade is incomplete. But this fact could be bended as seen in the crossover special "Ben 10/Generator Rex: Heroes United", where Upgrade merged with Rex Salazar's Nanoites to greatly enhance his ally's Nanoite-based machines during their fight Alpha-Omega. Compared to his look from the original series, Upgrade's appearance in Ben 10: Ultimate Alien had him with a black and green color scheme; he still has the green stripes on the black side, but now has black stripes in the green side.