Senbei Norimaki visited Metropolis Island when he was a kid. He remebers that the city was particularly scary, but he can not remember why. Senbei (in fact a robot designed to look similar to him) visits Metropolis Island again, along with Arale Norimaki, Gatchan, Chivil, and Oinkety Oink. The group travel form Penguin Village to Metropolis Island on Taxi Dragon's back in order for Senbei to show one of his creations in a TV broadcast. While he is in the TV station, Arale, Gatchan, Chivil, and Oinkety Oink play war outside and destroy the city.
In a filler episode, Arale, Senbei, Turbo and the Gatchans crash land in Metropolis Island because of a brainwashed Obotchaman. Dr. Mashirito (who had returned from being killed by escaping hell) roamed Metropolis Island being chased out by Chivil in an attempt to return his soul back to hell. Arale and Obotchaman proceed to have a battle, launching into buildings and causing havoc in the city before evacuating it.