In his first appearance, Don Slime is shy and awkward. Don's initially is just a simple black blob with eyes. His look seems to change with the amount of power he releases.
He is later revealed to be the King of Blue Grill, one of the kingdoms of the Gourmet World. Don also oversees the cooking competition in Blue Grill.
When Neo is revived, Chichi states that the only person who can go toe to toe with him is Don Slime. Chichi also says that Ichiryu's gourmet demon was in fact Don Slime.
Don then awakens his power and prepares to confront Neo. He gains a second form in which he becomes much larger and adds a beard and mustache. Don's face becomes more fleshed out with a nose and a mouth filled with sharp teeth. His behavior in his second form is much more violent and outspoken, and he acts recklessly.
In pursuit of Neo, Don jumps from Area 6 to the moon in a matter of seconds, then jumps off the moon destroying it in the process. He sights Neo and hurtles toward him. Their clash creates a huge release of energy.