Arale Norimaki -- AKA: Arale-chan. The little girl robot that Senbee creates in volume one. While she is supposed to be perfect, her eyesight is bad, and she has no common sense.
Ga-chan -- speaks in nonsense peeping that only Arale can interpret, and will eat anything, including dirt, but with the exception of rubber.
Niko-chan -- The king of the Niko-Chan planet. He and his servant wanted to take over the world, but Gacchan ate their spaceship so they had to stay on Earth. Senbe later let them test a spaceship and they went home.
Kinoko Sarada -- A parody of a popular Japanese marketing character. Runs away from home to become a biker mama when her father eats the strawberries off her dessert. Wants to be a tough girl, but can not deal with Arale or Ga-chan.
Pisuke Soramame -- Tarou's wimpy little brother. Always wears a cat-ear hat.
Daigorou Kurigashira -- Big Almond Head Gorou. A new teacher at Arale's new high school. Although his head is 5 times bigger than his body, he considers the rest of Penguin Village to be weird. His favorite form of punishment is "Punishment of Love", where he bops someone with his forehead.
Betty -- A pig from the neighboring village
Caramel-man: AKA Obotchaman -- A naive, idealistic robot made to stop Arale "from conquering the world." Looks like Astroboy, is much more polite than Arale, and is her exact match for power. Instead, Obotchaman develops a crush on Arale, and is attacked by Mashirito.
Unchi-kun -- Mr. Shit. An animated coil with feet. Kind of a running gag. Seen occasionally in most volumes. His origins are given in volume 14 (Senbee had to take a "relief break" while driving through the woods on the way towards town.) Unchi-kun wanders into town, is discovered by Arale, and taken to the Norimaki's home to live in the toilet bowl there.
Suppaman -- Parody of Superman, this guy eats umibochi (tart pickled plums (suppai means 'tart' or 'sour',)) to gain his great powers. In actuality, he's a short, stocky, cowardly braggart who likes using a gun and handgrenades to solve personal problems. Claims to be working for world peace.