Ohanian talks about how Y Combinator helped shape the idea for Reddit in the early stages:
We approached Y Combinator … with an idea that would transform the way you order food, specifically using a cell phone to do so. They didn’t really like the idea. They liked us, but they hated the idea.
They still didn’t have a firm idea, but sat down with Graham and talked about a site that would filter the most interesting web content.
…it was in that conversation with Paul where we developed this idea for creating a way to find out what’s new online.
The idea morphed into the final product:
All the actual mechanics of how that would work, basically happened in the next few weeks, while Steve [Huffman] and I were in a crap apartment, in Bedford, Massachusetts, playing a lot of Warcraft.