All the girls in the Aasu family are named after numbers: Hitomi (hito, one), Futaba (Futa, two), Mitsuki (Mitsu, three), Shii (Shi, four), Itsue (Itsu, five), Mutsumi (Mutsu, six) and Nanase (Nana, seven). As well as this, Hitomi means "eyesight" or "eye" in Japanese, which describes Hitomi's power (precognition, sixth sense).
The Aasu sisters' given names contain number puns, from youngest to oldest: hito(1), futa(2), mi(3), shi(4), itsu(5), mutsu(6), nana(7).
Many of the characters are references to characters in Excel Saga, which was done by the same staff and cast.
All the music (except for the opening, ending theme, and a song sung by Yumiko Kobayahsi in the 2nd episode) is recycled from Excel Saga.
At the end of the scene where K learns he's an alien, look for Menci (Excel Saga) on the table.