Penguindrum (TV)

Ringo and Momoka Oginome are sisters with similar names. Ringo means "apple", while Momoka means "fragrance of a peach"

In Ep 6 (during the flashback) Ringo has a death note on her desk.

Without spoiling too much, the date March 20, 1995, holds significance for every member of the cast. In real life, that was the day that members of the Aum Shinrikyo sect released sarin gas on the Tokyo subway, killing thirteen and injuring thousands more.

The stations that appear in the show are all on the Marunouchi Subway Line (丸ノ内線); one of the main lines of the Tokyo Metro system. It was also one of the lines affected by the 1995 Sarin gas attack perpetrated by the Aum Shinrikyou cult. All the stations on the line are usually depicted on official maps using a capital or small letter M followed by a number.

In Episode 8, starting at around the 9 minute mark, the two minute long western themed sequence plays multiple homages to the "Man With No Name" or "Dollars" Trilogy series of spaghetti westerns starring Clint Eastwood. Much of the framing of sequences and fonts are reminiscent of the genre, along with much of the clothing. Specifically, Ringo's outfit is almost an exact match for Clint's in that trilogy of movies. The distinctive duster worn by Yuri Tokikago is the same style as the one worn by Lee Van Cleef in For A Few Dollars More(1965). Ringo's shootout sequence against Yuri has Ringo popping back up, much to Yuri's shock, then revealing that the diary was used as a bullet plate. In A Fist Full of Dollars(1964) Clint's character uses a steel plate over his heart to protect himself from bullets in much the same manner. The theme of Keiju Tabuki precariously balancing with a noose around his neck while Yuri shoots the rope is reminiscent of The Good, The Bad, and The Ugly(1966), where Clint's character was responsible for shooting and cutting the rope of would-be recipients of the hangman's noose. Also from the same movie, Yuri's representation as "The Bad" being shot into a grave by "The Good" is similar to events in the finale.

In episode 9, the girl mentions the story “Hadashi no Gon” at about 15:05. This is a reference to the 1973 manga “Hadashi no Gen” (はだしのゲン, Barefoot Gen) by Nakazawa Keiji which chronicles the Hiroshima atomic bombing disaster.

In Episode 9, shortly after the four minute mark, two of the books Himari is returning are entitled "Christine" by "Stephen Queen." This is a reference to the horror novel "Christine" written by famous novelist Stephen King and published in 1983.

In Episode 10, following the chase through the sheets in the 14 minute mark, the song used to torment Kanba Takakura is the second movement ("Largo") from Antonin Dvorak's 9th symphony, "From the New World."