Arnold is the son of Miles and Stella Shortman, a pair of adventurous scientists/doctors who assisted the Green Eyes of San Lorenzo’s rainforests. He was born a few months after the pair retrieved a valuable artifact from the river pirate La Sombra: the Corazon, a sacred jewel that glows green but is said to be too sacred to gaze directly upon.
Arnold’s beginnings are the stuff of legends, perhaps a portent to just how different he would grow up to be. He was born during a volcanic eruption in one of the Green Eyes’s temples, his parents and their friend Eduardo having been led to safety by green smoke. The eruption seemed to grow more intense as Stella’s labor pains grew worse, and magma surrounded the temple, cutting off all escape. Then, at the sound of Arnold’s first cry, everything just…stopped. The eruption abruptly ceased, and all of nature was quiet. His parents called him a miracle baby.
At first, the family continued living in their little hut on the edge of the rainforest, apart from the main town. However, this changed when one night, while his parents were sleeping, Arnold crawled out of bed and outside. His parents were frantic and panicked when they saw him fearlessly approach one of the local snakes. After retrieving him, they decided to move back to Miles’s hometown of Hillwood back in the US.
They ended up living with Miles’s parents in their boarding house, Phil and Gertie more than happy to welcome the family. Perhaps a few months later during a trip to the playground, Miles gave Arnold his first hat, a small blue baseball cap that Arnold would become very attached to. It was at this time that his parents swore an oath never to let him out of their sight again when he climbed to the top of the slide when they weren’t looking and slid down into his frantic mother’s arms. For almost two years, their lives were filled with happiness.
One day, however, Eduardo came to visit with terrible news: Their friends, the Green Eyes, had come down with a sleeping sickness which Stella had cured them of once before. At first, Miles and Stella hesitated, not wanting to leave their son behind. However, the Green Eyes-though they’d never truly seen the mysterious people before-were dear friends who’d saved them just as many times as they had saved the Green Eyes. In the end, they decided to go, intending to return swiftly.
But when they left that October 5th, they never came back.
Phil and Gertie took over raising Arnold, Phil telling him fantastic stories about his parents that were both true and made up. Gertie would play lots of make-believe games with her grandson, being somewhat of a child at heart herself.
At around age 3, Arnold was sent to Hillwood’s Urban Tots preschool where-on the first day-he accidentally charmed a little blonde girl with a pink bow by sheltering her from the rain with an umbrella and complimenting her bow. He even gave up his crackers to her when hers got stolen by a bully though, shortly afterward, Helga G. Pataki would become a bully herself to hide her crush on the weird-headed boy.
Over the next seven years, Arnold grew up with the same kids he met in preschool, remaining best friends with Gerald Johansen. He passively accepted the torment that Helga kept throwing his way, completely unaware that she had feelings for him. Throughout all of growing up in the big city, Arnold remained an optimistic daydreamer, ever watchful for the day his parents would walk through the front door.
It was in fourth grade that just how different he truly was started being noticeable. He eventually stopped daydreaming, focusing more on the people around him. He figured out he had a knack for helping people in distress whether it was helping a boy who’d been terrified of ever leaving his stoop take that first step off (“Stoop Kid”) to finding the document that proved his neighborhood was a historic landmark and saving his home from a developer’s wrecking ball (Hey Arnold! The Movie).
However, time eventually did wear him down, and he decided to pack away his hat along with all his memorabilia of San Lorenzo on the seventh anniversary of his parents’ disappearance. He barely remembered them aside from stories and he told his grandfather that he was tired of holding out for something that obviously wasn’t going to happen. However, while putting the boxes in the attic, he accidentally discovered his father’s journal, left behind from just before he and his wife left. While reading it with his grandmother and grandfather, Arnold learned the truth behind the stories his grandfather had told him. Then while reading through it privately a second time, he discovered a map, quite possibly leading to their last known location. (“The Journal”)