It seems to use %s.jpg as a filename and to request the browser to download the picture you clicked on as that filename, so probably some larrikin typed 2girls1cup in as a prompt and you happened to click on whatever picture came out and was in the feed.
> Larrikin is an Australian English term meaning "a mischievous young person, an uncultivated, rowdy but good hearted person", or "a person who acts with apparent disregard for social or political conventions".