All of the sisters in the Aasu family are named after numbers and their names contain number puns, from the youngest to the oldest: Hitomi (hito, 1), Futaba (futa, 2), Mitsuki (mitsu, 3), Shii (shi, 4), Itsue (itsu, 5), Mutsumi (mutsu, 6) and Nanase (nana, 7). In addition to this, Hitomi also means "eyesight" or "eye" in Japanese, which describes Hitomi's powers (precognition, a sixth sense).
The series was originally based on an inside joke from one episode of Excel Saga; director Shinichi Watanabe decided to take said inside joke to its most extreme logical conclusion, thus creating the series.
Many of the characters in this series are references to characters in Excel Saga, which was made by the same cast and staff.
All of the music in the series (except for its opening theme, its ending theme, and a song sung by Yumiko Kobayahsi in the second episode) is recycled from Excel Saga.
At the end of the scene where K learns that he is an alien, Menci (Excel Saga) can be seen on the table.