Ahegaokin (アヘ顔菌, roughly meaning: ahe face bacillus) is a meme that originated in 2008 with a drawing of Patchouli Knowledge by yukiman (post #319291), which was subsequently parodied by many other artists.
A photoshop of Suiseiseki from Rozen Maiden making this face (post #410670) became a popular variation of this meme on 4chan, but it is not the origin.