J'oh can mix 54,382 different kinds of drinks, from Abraxan Blue Lava Fireballs to Zygotic Fermented Slime Slurpees. However, like most of the patrons of the Black Hole Bar and Grill (where he tends bar), he is violently robophobic. A member of an unspecified alien race, he has numerous blue tentacles, a huge fanged mouth, and odd blue lumps on top of his head.
Marvel comics continuity
When Landmine and Cloudburst came to Grand Central Space Station to buy microchips, the Black Hole was one of their first stops. There they witnessed J'oh refusing to serve a Chromite robot. Despite speaking up for him, and participating in the ensuing brawl, they were unable to stop J'oh and a few others from throwing the Chromite out the airlock. J'oh allowed the Autobot Pretenders to stay and finish their drinks, after he was convinced they had no special love for robots. (The Chromite was later devoured by the Mecannibals.)
Soon, the Nebulan Powermasters Hi-Test and Throttle learned that Landmine and Cloudburst were in fact robots inside their Pretender shells, and stated, "We must notify J'oh -- immediately!" When the Autobots subsequently showed up at the bar, the Nebulans were watching, and Throttle mentioned that he gave J'oh "the same [payoff] as I gave him for the Chromite." J'oh promptly denounced the Autobots as "rust-sucking scrap-heaps" and, like the Chromite, they got thrown out the airlock. There, they were captured by the Nebulans and delivered to the Mecannibals.
Though it is not made absolutely explicit, it seems clear that the Nebulans and Mecannibals have an arrangement with J'oh, where the bartender throws robots out that specific airlock, so the Nebulans can capture them, and deliver them to the Mecannibals to be eaten.