Although featured on the promotional poster, Tarou Soramame does not appear in "Dr. Slump & Arale-chan: Hoyoyo! The City of Dreams, Mechapolis." Within the broader Dr. Slump series, Tarou emerges as a rebellious teenager in Penguin Village, distinguished by his perpetual wearing of sunglasses. He befriends Arale following her school enrollment, alongside classmate Akane Kimidori. Senbei Norimaki initially perceives him as a negative influence due to his defiant demeanor. Later in the series timeline, Tarou joins the Penguin Village police force. This career transition precedes the Dragon Ball crossover event where Arale assists Goku during the Red Ribbon Army storyline.