WRONG
The sorting hat was never wrong.
It could see into the minds of any human being whose head it sat upon, it could analyze personalities, correctly place anybody in a house.
The sorting hat was always correct.
Students always suited their houses perfectly; nobody ever had to complain.
The sorting hat was perfect.
So of course, it was very confident in itself. Back then, when it had been young, it had sorted students in mere moments, sure that its choice was right.
It had seemed natural to sort Peter Pettigrew into Griffindor.
The boy was meek. He had needed friends for protection. Friends that would be by his side always.
And the sorting hat had assumed that the boy would be just as loyal.
And so, many years into the future, the sorting hat was extremely surprised to hear that Peter had gone nasty.
Nobody ever blamed the sorting hat.
But they just had to keep talking about it, didn't they? Discussing it, right there where the sorting hat could hear them.
The sorting hat vowed that it would never fail again.
If there was a possibility that a child should be in Slytherin, so they would be sorted. There would be no more failure. No more death.
And so the sorting hat's record of perfection continued.
Notes: I get my best ideas in the shower. Uh. I just kind of imagined the sorting hat wouldn't exactly feel happy about that whole thing. And if Peter had been in Slytherin, he wouldn't have been friends with the Potters, so he couldn't have killed them. …So yeah. The sorting hat is fun to put emotions into. …Yeah. I hope I kind of got the effect I was looking for. 3