Twitch Plays Pokemon

How does the twitch chat control the game? Is it seriously one person trying to keep up with all the input spam or is there some program that essentially reads the inputs and tries to input them as fast as the game can handle them?

Twitch chat is available via IRC (or was). Various tools exist on the web that allow you to grab the chat. They then take the chat and run it through a script that strips everything but "up down left right start select". The chat is then read as commands for the game via a different script probably and displayed on the screen via another tool of some sort.

Basically, no there isnt a monkey hammering away on a keyboard that moves the character. It's all done by the chat.