A strange and mysterious meme. Posted here upon request and because other posts (comment #208130, comment #209682) reference it.
The tale of its origin, in moon language: 元ネタはpeercastの配信者の一人のアレミのリス>>ナーがこのAAをつくり、アレミスレに投下されたの>が初出。 アレミがあまりのシュールさに爆笑してスレのテン>プレに入れ、 それがpeercastの東方配信者間で流行り、その後>>peercast全体と2chとに波及したという 説がある (このスレッドのcomment #219の書き込み情報より)
Story goes that someone's radio show received this fanart from a listener; the host decided it was so weird and funny that she uploaded it to her site, and people immediately ran with it.
A meme involving giant, disfigured heads resembling those of Touhou characters. It originated on 2ch in early 2008 when an Anon tried to make a Shift_JIS portrait of Reimu and Marisa and failed horribly. Another Anon thought the failed attempt was humorous and drew the infamous original picture. Their catchphrase "Yukkuri shiteitte ne!" literally means "Do it slowly!", but has been more loosely translated as "Take it easy!" (edited for tl:dr factor)