Jax is an anthropomorphic periwinkle cartoon rabbit whose design evokes the look of early cartoon characters, also known as "rubber hose" characters. He has long bunny ears on the top of his oval-shaped head, and his overall build is tall and slender, with a rather long neck. Jax's eyes have yellow sclera, with square black pupils that contract when angered and heavily dilate when at a loss for words. Jax's yellow teeth usually have a flat shape to them, but when his mouth is opened, his teeth appear sharp and jagged. Jax has thin eyebrows that appear in the majority of the scenes. In "They All Get Guns" (episode 6) Jax has a small, spherical tail where previously he didn't. Jax ocasionally is shown without a his yellow teeth out.
Jax wears light, pink-colored overalls and pale-yellow gloves. His overalls have yellow buttons on them and also have a single lighter pink rectangular pocket on the front and lighter pink sections on the bottom hem of his overalls. He is usually barefoot.