Four Arms is the Omnitrix's DNA sample of a Tetramand from the planet Khoros.

Four Arms is a humanoid alien that is twelve feet tall.[CN 1] He has well-developed muscles, two pairs of four-fingered arms, and dense armor-plated red skin.[CN 2] A black stripe goes from his chin to his lower lip, and he has four eyes: a main pair and a smaller pair below them, while he lacks ears or nose. He has whisker-like spikes on each forearm and two-toed feet.

In the Original Series, Four Arms wore a white T-shirt with a black line going down it and black pants with a strap on each foot that reveals his two toes and the back of each foot, and black fingerless gloves. He wore the original Omnitrix symbol on his upper left shoulder. His eyes were orange-yellow, and he had no hair.

In The Krakken, Four Arms donned muck and vines to appear as a lake monster.

While under the effects of a cold in Side Effects, his skin turned from red to a sickly shade of red-orange, and he develops pungent hives in his armpits.

In Game Over, while inside Sumo Slammer Smackdown, Four Arms wore brown shoulder pads and knee pads, grey armor under his shoulder pads as well as black pants. He wore the Omnitrix symbol on a hat on top of his head.

In Don't Drink the Water, 4-year-old Four Arms was slimmer than his 10-year-old self and had a bigger head and eyes.

In Destroy All Aliens, Four Arms remained the same except he had pale red fingernails, and his clothing had some type of fabric on the black stripe.

In Ultimate Alien, 16-year-old Four Arms wore gold wrist and ankle bands, a pair of black underwear that has a gold waistband, and two golden sashes that went across his chest. His eyes were recolored green, he had a black ponytail, and he wore the Ultimatrix symbol on his chest.

In The Forge of Creation, 10-year-old Four Arms looked exactly the same as in the Original Series except the Omnitrix symbol was recolored green.

In Heroes United, Four Arms, in addition to his clothes in Ultimate Alien, wore pants and fingerless gloves and had tattoo-like stripes on his body, making him look somewhat similar to his Original Series design.

In Omniverse, 11-year-old Four Arms looks similar to his Original Series design, except his eyes are recolored green, his skin is a lighter tone, and he has a second set of pectorals for his other set of arms.

16-year-old Four Arms has three short spikes on the top of his head, a mustache-like design, the black stripe on the top of his head is replaced with small spikes and the same second set of pectorals as his 11-year-old self. He has no hair and wears a black tank top-like shirt with one large green stripe in the middle, black pants, a green and white belt where the Omnitrix symbol is located, and black fingerless gloves with green cuffs at the wrists.