Seven of Seven

Seven of Seven (七人のナナ Shichinin no Nana) is an anime series that debuted in 2002. It's what happens when you let Yasuhiro Imagawa (Giant Robo, G Gundam) create a Shoujo series.

Nana Suzuki is an ordinary schoolgirl with a crush on one Yuichi Kamichika. One day, while trying to bake a cake for Yuichi, she stumbles on her scientist grandfather's secret experiment to separate the light of a rainbow into seven crystals. Naturally, the experiment goes awry, and splits Nana into seven versions of herself, each with her own matching rainbow crystal. Now, Nana must find a way to integrate the crystals together, or else all seven of her will vanish.

The Seven Nanas are:

Nana: The ~~Original~~ Responsible Nana.
Nanappe: The Bokukko Nana.
Nanakko: The Slacker Nana.
Nanacchi: The Cheerful Nana.
Nanarin: The cry-baby Gamer Chick Nana.
Nanasama: The Bookworm Nana.
Nanapon: The Weird Nana.

Tropes used in Seven of Seven include:

Balloon Belly: Nana in the DVD episode.
Cloning Blues
Color Coded for Your Convenience: The seven Nanas.
Crossover: Mutsumi and the Hinata's house ghost, who had already appeared in the Keroro Gunso manga, made their first animated appearance in the Seven Of Seven anime.
- On the other hand, Melody Honey, who debuted in this series, goes on to appear in both Keroro Gunso and Arcade Gamer Fubuki.
Evil Twin: An eighth Nana, Jamanana. In the manga, Nanacchi, of all the Nanas, was the mean one.
The Danza: Nana Mizuki (the Original Nana)
Henshin Heroines: Their crystals turn a group of Sentai costumes in legitimate Nanaranger suits.
Hive Mind: The six other Nanas tend to act as one person.
Hotter and Sexier: The manga.
Les Misérables: Nanasama's favorite book.
Literal Split Personality
Me's a Crowd
Rainbow Motif: With indigo switched out for kimidori (yellow-green), as is to be expected in a Japanese rainbow.
Red Oni, Blue Oni: Nanappe is hot-tempered, violent, and wields the red crystal. Regular Nana is much more calm, rational, and level-headed, and wields the blue crystal.
Sentai: The seven Nanas can become the seven Nanarangers.
Seven Is Nana
Talking to Herself: The English dub, if one considers all seven Nanas as different people. The Japanese version uses a different actress for each Nana.
Two Girls and a Guy: Nana, Hitomi, and Yuichi in the manga, where the three are childhood friends.