Harry wasn't an only child, but had an identical twin, who died at birth. He's been hanging around ever since.
The zoo was crowded with families, it being a most pleasant Saturday morning. The Dursleys bought Dudley and Piers large chocolate ice creams at the entrance and then, because the smiling lady in the van asked Harry what he wanted before they could hurry him away, they bought him a lemon ice pop, the cheapest item on the menu. It was actually fairly good, Harry found.
James waited until Harry had finished his treat before deliberately floating through their cousin. Dudley gasped and jumped at the sudden frozen feeling in his guts, dumping his ice cream into the dirt.
The ghost laughed himself silly, as Harry turned his face towards the gorilla exhibit they were in front of to hide his twitching lips.
They ate lunch in the zoo restaurant. Still pouting over the loss of his last ice cream, Dudley had a tantrum because his knickerbocker glory didn't have enough ice cream on top of it. Harry wasn't surprised that Uncle Vernon bought him another one, but astonished was too mild a word when he was allowed to finish the first one.
All in all, it was the best time he had ever spent with his family, and for once James was having just as much fun as he was.
He really should have known it was too good to last.
After lunch they went to the reptile house. It was cool and dark inside, an abrupt change from the sunshine outside, and Harry lagged a bit behind the others as he waited for his eyes to adjust. There were lit windows all along the walls, behind the glass of which all sorts of lizards and snakes were crawling and slithering over man-made habitats of wood and stone. Dudley and Piers wanted to see huge, poisonous cobras and thick, man-crushing pythons; Dudley quickly found the largest snake in the building. It was enormous- Harry was certain it could have wrapped its body twice around Uncle Vernon's new car and crushed it utterly.
Except... it didn't look in the mood to do any such thing. In fact, Harry was equally certain it was asleep.
His disappointed cousin stood with his nose pressed against the glass, staring at the python's glistening brown coils.
"Make it move," he whined at his father. Vernon tapped on the glass, but the snake didn't even notice.
"Do it again," his son ordered, but rapping smartly on the glass with his knuckles didn't produce any better results.
"This is boring," Dudley moaned. He shuffled away to the next window, Piers close behind him. Apparently, being in a dark room with Harry somewhere behind him was spooking the boy just a little.
Holding back a chuckle, Harry moved up to the tank his cousin had just left, his twin floating along behind him. He peered inside at the snake, pressing his palm flat against the glass.
"Sorry about him," he murmured, "He's an idiot. He doesn't understand what it's like, being stared at day in and day out, like you're some kind of freak..."
James stared at him, looking as confused as Harry had ever seen his brother.
"Harry," he asked slowly, "why are you hissing at the snake?"
The boy blinked at him. "Huh?"
Suddenly there was a tap on the glass that made them both jump. They turned to find the python practically eye to eye with them, not only not asleep, but very, very awake.
And then, /it winked/.
The two Potters stared at it, astonished. After a moment of sheer disbelief, Harry looked around to see if anyone was watching, a bubble of what almost felt like glee welling up inside him. No one was. Harry looked back at the snake and winked, too.
The snake jerked its head toward Uncle Vernon and Dudley, then lifted its eyes to the heavens, a look that said more plainly than they'd thought possible: /I get that all the time/.
"I know," Harry murmured in response. "It must be really annoying."
The snake nodded vigorously.
James glanced at him sideways.
"You know, you're hissing again," he said, "It's kind of creepy."
Harry gave him an annoyed look and turned back to the snake, "Where do you come from, anyway?" he asked.
The python jabbed its tail at a little metal sign next to the glass, and Harry peered at it to read what it said: /Boa Constrictor, Brazil/.
"Brazil, huh? Was it nice there?"
The snake jabbed its tail at the sign again and Harry read on: /Raised in captivity/. "Oh... so, you've never been to Brazil?"
The boa constrictor shook its head. Harry was about to ask it another question, just because he could and to make James' eyes bulge even more, when a deafening shout came from behind them.
"DUDLEY! MR. DURSLEY! COME AND LOOK AT THIS SNAKE! YOU WON'T BELIEVE WHAT IT'S DOING!"
Harry spun and glared daggers at Piers, who paled dramatically. Dudley came waddling towards them as fast as he could.
"Out of the way, you," he said, punching Harry in the ribs. The breath came out of the boy in a rush as he fell hard to the concrete floor. What happened next came as a surprise to all of them.
Both Dudley and Piers were leaning up against the glass, peering inside, when abruptly the glass simply /vanished/. Piers jumped back just in time to stay on his feet, but Dudley wasn't so lucky; he tumbled forward, making a splashy landing in the artificial pond.
Inside the cage.
For a long moment, nothing else happened. Then the great snake began to uncoil its enormous length, unsnarling coil after coil of muscle and scales. It slithered out onto the floor as the people throughout the reptile house began to scream, only just starting to realize what was happening.
The boa constrictor paused for a second in front of Harry, studying him with fathomless black eyes. Then it inclined its head.
"Thank you," Harry heard, and then he and his stunned brother were watching it slither away from them, while Dudley screamed behind them as he discovered that the mysteriously-vanishing glass was back in place.
"Brazil, here I come..."