Little Harry Potter thought that nothing could possibly ruin his day. For the first time in his life, he was on a proper outing, and to the zoo even! True, Dudley didn't want him there, and Aunt Petunia and Uncle Vernon didn't buy him very much for lunch (they wouldn't have bought him anything if not for the funny looks they'd get otherwise). And he supposed he looked silly in the small circus tent of a shirt he'd inherited from his large cousin, with his trousers cinched up underneath nearly at his chest. Even so, he was at the zoo, and nobody would ruin it for him!
Harry briefly considered heading toward the reptile house next, as like most ten (almost eleven!) year old boys, he thought snakes and lizards were almost the most brilliant animals ever. But he already saw Dudley waddling off in that direction with his ratty friend Piers slinking behind him, so he decided to give it a miss for now, and headed over toward a red, eastern-style bridge he'd heard Uncle Vernon muttering something unpleasant about earlier. To his mind, this just meant the Dursleys were likely to leave it - and him - alone.
When he reached the red painted bridge, he stood on tiptoes to try and peer over the side. Sadly, he was still too small to see much over the edge. Nearby, it sounded as though a nice sounding lady working for the zoo was talking about whatever was in the water.
"Below," the lady said, "are something called Koi fish. Koi fish are very special, and one of the most fascinating things about them is that they keep growing until they can't get enough food in their environment. So, a Koi in a small bowl that's not given much to eat is a very tiny fish, but one let into a large lake will grow to dozens, maybe a hundred times that size!"
Other kids on the bridge made noises of awe at this, and Harry decided to scramble up onto the railing of the bridge so that he could see. He wanted to see a big fish!
Not a minute after he'd clambered up, leaning further out than he probably should have, he felt a hard shove at his back. With a frightened shout, Harry toppled off the bridge and into the fishy water. Sputtering and making faces at the taste in his mouth, Harry scowled up at the bridge where he saw Dudley and Piers laughing and pointing down at them. The nice zoo lady was looking down as well, and after seeing he was alright grabbed his cousin and Piers by the arms and marched them away, asking about their parents.
Down in the muddy water, Harry glanced down at his hands to make sure he got up safely, and finally got a look at a Koi fish. It was a tiny little thing, barely as long as his pinky (and his hand was really quite small itself). He could see further away a bunch of big shapes in the water.
"We're just alike, you and me," he muttered at the tiny fish. "I bet those big fish over there hog all the food and pick on you all the time right?"
The fish, being a fish, didn't answer. Harry nodded anyway, and stuck his pinky out at the fish.
"But we'll show them one day, right? It's a promise."
Inexplicably, the tiny fish swam forward and rubbed his pinky, like it was agreeing with the plan. Harry grinned a bit, and slopped his way over out of the muck. He couldn't explain it, but when the fish touched him, he'd felt a tingle seem to zip through his entire body. Almost the same thing that he'd felt when he somehow traveled to the roof of his school, or turned his teacher's hair blue.
The Dursleys were, after the zoo lady found him again, asked to leave because of the disruption. Dudley blamed Harry entirely, of course, and the Dursleys sided with him as usual. While Dudley was comforted with new toys and more sweets, Harry spent a sad few weeks mostly locked up in his tiny cupboard with little food, for "ruining Diddy's outing."
Harry sighed to himself in the tiny room, thinking of what the zoo lady said, and picturing a tiny black Koi fish with a lightning scar in a tiny, tiny bowl.