Disclaimer: I do not own Harry Potter.
A/N: I thought this was funny, but I'm not sure that I conveyed the joke right.
"Potter, Harry!"
Eleven year-old Harry Potter approached the stool cautiously. As he did so, movement caught his eye, and he glanced at the end of the table. It was the hook nosed, greasy haired visage of Severus Snape that had caught Harry's eye. He looked away quick, knowing from the sneer that even if Harry wasn't James Potter, then he, Snape, would have no problem dealing with him. As Harry turned to sit, he smiled at the familiar dark red hair of his mother in her place as the Muggle Studies professor. They exchanged quick grins before Harry sat down.
The Hat's brim obscured his vision as it came to rest on his nose and Harry crossed his fingers. "Hello, Harry Potter."
"Hello, Mr. Hat," Harry replied silently. "I'd really like to go to Gryffindor, or Ravenclaw, but I wanted to ask a favor first."
"What favor is that, Mr. Potter?"
"Well, my dad really doesn't like Professor Snape and Snape hates my dad, so maybe you could pretend like you're gonna sort me in Slytherin, and then change houses." Harry replied, "It would be a great prank, please?"
"What a brave Gryffindor you are, Mr. Potter. Are you ready? Here we go. I'm sure you'll be happy in…" The Hat took a deep breath, "Slytherin!" Harry pulled the Hat off and turned to look at Snape, the man looked ready to faint. "Wait, no, I meant GRYFFINDOR!" The Hat cried, loud enough to shake dust from the rafters.
Either that or the thud of Snape's head connecting with the ground was hard enough to send dust flying.