Upchuck has green skin, six sprout-like growths on the back of his head, a dark-green patch of skin on his head, light-green skin on his face, neck and belly and crooked teeth. He also has a green tail.
In the Original series, Upchuck wore a black open-front suit with white over-sleeves and white bands around his legs and white padding under his three-toed feet and wears the Omnitrix symbol on his left hand.
In Alien Force and Ultimate Alien, Upchuck wears the Omnitrix/Ultimatrix symbol on his tummy.
Upchuck has four very strong, adhesive tongue that can stretch to great lengths, allowing Upchuck to latch onto large objects and reel them in with relative ease. Upchuck's mouth and stomach can also stretch, allowing him to swallow and digest objects fairly larger than himself.
Upchuck possesses several acid-filled stomachs that dissolve almost all forms of matter. The items ingested are converted into explosive balls of liquids that can be expelled with great accuracy. He can also make them curve, like a boomerang, shuriken or frisbee.
Upchuck is able to take a surprising amount of punishment for a creature of its size, taking the force of a moving car impact as well as surviving after being thrown through a wall.