I hope you are sitting down for this... "2 Girls One Cup" is, according to the definition on Wikipedia, "the unofficial nickname of the trailer for Hungry Bitches, a scat-fetish pornographic film... The trailer features two women conducting themselves in fetishistic intimate relations, including defecating into a cup, taking turns ostensibly consuming the excrement, and regurgitating it into each other's mouths".
Part of what has facilitated 2 Girls 1 Cup's spread are the reactions it causes. Thousands of videos exist on YouTube of users showing the original video (off-camera) to their friends and taping their reactions, although some videos seem to be staged.
The visualization project with the same name [paulshen.name] attempts to analyze these reactions, in terms of both audio and video. A collection of 20 of the most-viewed YouTube reaction videos were downloaded and then edited to start at the exact same time. Each of these videos were then processed to collect data about optical flow (e.g. amount of motion between consecutive frames) and volume (e.g. fast Fourier transformation of the audio instance).
The author expected that by analyzing the reaction videos quantitatively, meaningful patterns would emerge that could, in an indirect way, describe 2 Girls 1 Cup trailer. But it appears that once the mayhem begins, the reaction videos turn into chaos, maintaining the shock through the duration of the video.
You can watch a compilation of all the viewers' reactions (and *only* the reactions) below.