ケツ妹子
Ketsu-Imoko, Butt Imoko appeared in one of the episodes of [[Gag Manga Biyori]].

From [[Gyagu Manga Biyori|Japanese historical texts]].  "Shoutoku Taishi":http://en.wikipedia.org/wiki/Prince_Sh%C5%8Dtoku, traveling with "Ono no Imoko":http://en.wikipedia.org/wiki/Ono_no_Imoko, is having trouble writing his letter to the emperor of "Sui":http://en.wikipedia.org/wiki/Sui_Dynasty, and briefly considers writing about his strange dream the night before.  This is depicted as a torso-less Imoko with his head attached at the abdomen and "butt imoko" written next to him.  Imoko rejects the idea, which unfortunately leads to the "infamous opening":http://books.google.com/books?id=LipE-1U6-Q0C&pg=PA141 that refers to Sui as "the land of the setting sun" being written instead.
butt imoko