A professor and a genius, Professor Genius is something of a right-hand man to King Morpheus. He tries his best to help and watch over Nemo, particularly making sure he avoids Flip. He is extremely well mannered and though he tries to maintain a formal front wherever he goes, the Professor can't resist the urge to dance whenever the chance presents itself.
The king of Slumberland and the Princess's father. He ordered the Professor to bring Nemo to Slumberland to be his daughter's playmate. He shares an interest of trains and machinery with Nemo, who grows very dear to him. The king, in spite of his expected responsibilities, has a habit of sneaking off to his playroom (where he accidentally runs into Nemo who, at the time, wasn't aware of who he was). Morpheus decrees that Nemo is to be trained to be Prince of Slumberland and gives him "The Golden Key" which can gain him access to anywhere in Slumberland (provided Nemo promises not to open the door with the same symbol as the key on it). He gets kidnapped by the Nightmare King at Nemo's coronation, prompting Nemo to set off after him, along with the Princess, Prof. Genius, Icarus, and Flip.
The story's main antagonist. He was sealed behind a large door long ago, until Nemo, under Flip's misguided influence, accidentally releases him. He kidnaps King Morpheus in order to lure Nemo, and more importantly the Royal Scepter (which he and the other inhabitants of Nightmare Land fear), to his Nightmare Castle. Nemo barely manages to destroy the Nightmare King with the scepter and ends the evil king's reign along with Nemo's own nightmares.
Incredibly fast and unbelievably ruthless, Little Boy is the perfect partner for Fattmann in committing the Machine Corps' atrocities. With molecule-thin wire cutters embedded in his fingers, he cuts through opposing troops as if they were made of butter, leaving still wriggling piles of dismembered corpses in his wake. There is only one thing in the universe he fears… the Spriggan. (Source: Angelfire)
Father of Sue who is a cop. He becomes the leader of the Wind people.
Called "Little Demon" by Soul Eater, he is a strange demonic imp that appeared before Soul inside his heart after his first encounter with Ragnarök. He told Soul "to be strong... follow me..." when soul decides to follow the imp states; "There will be insanity and ecstasy of joy." He may represent the power of the black blood and the insanity deep inside everyone's heart.