Mars (火星) is a planet in the North Galaxy. It is the fourth planet from the Sun and the neighboring planet to Earth II (just like its real life counterpart). It is apparently the home planet of the Martian race.
Mars II first appeared in the Dr. Slump during King Nikochan's first appearance where he uses his spaceship to destroy it to threaten Arale. Later on, the planet is mysterious revived from unknown means and appears again where it gets a big crack on its surface due to the fight between Arale and Dr. Mashirito's robot, Caramel Man 001.