In their native Hoenn, Aron are a pest, but not particularly dangerous, for metal buildings are regularly treated with chemicals to keep them away; they subsist on steel-types, scrap iron, and old silverware. Tragically, the same could not always be said of Unova, a land built on steel.
A large shipment of Aron to the Castelia Zoo escaped in the aftermath of an automotive accident. The driver quickly alerted the local authorities, and most of the Aron were captured before they could damage the city's tall skyscrapers. Yet a few of these pokemon escaped to the south of the city and, in the middle of the night, made their way to the top of the tall deck supporting the Skyarrow Bridge and began to chew. A few brave trainers tried to stop them, but they had walked high enough that only flying pokemon, who Aron resist extremely well, could reach, and they were able to shrug off the attacks until the bridge collapsed and fell, with the Aron, hundreds of feet into the water. One trainer was caught by their Unfezant, but the others, along with a few people traveling at night who had not reached the bridge's exit in time, fell to a watery grave.
Yet life goes on. A few years later, a new Skyarrow bridge was built, bigger and greater than ever, rededicated in honor of the dead. And although this bridge's cables are no more difficult for Aron to walk across than the old, and still touch the bridge itself at one point, the stairs leading up to the bridge are too steep for such a tiny pokemon to climb. The surviving Aron and their descendants have settled for the shore and water below, where pieces of the old bridge still provide an unending meal.
