Spitter is a dark green, circle shaped alien. He resembles a puffer fish. He has 3 spikes sticking out the top and the bottom of his head.
Spitter wore black trousers in the orignal series, and he wears the Omnitrix symbol on his stomach. In Ultimate Alien the bottom of his pants are white. In Ultimate Alien, He has green eyes and his teeth are now white. He now wears the Ultimatrix symbol on his stomach.
Spitter can spit out a concentrated blast of green slime at will. This slime is very slippery, and can be made acidic and has been shown to be highly conductive. Spitter has sharp teeth, enabling him to bite enemies. Spitter seems to have enhanced strength, as seen in Ben 10,000 when he held up Dr. Animo with a yeti body.