Disclaimer: If wishes were horses...
Open Your Eyes
1. Naturally, it was Matsuri that brought them all together. Their first meeting destroys half of Training Ground 15 and lands them all in hospital for four days. After that, they pretty much had to be friends.
2. However, it's Moegi who keeps them that way. She grounds Matsuri and frees Hanabi. More importantly though, she keeps them from killing each other.
3. Hanabi isn't sure if they need her. Matsuri says of course they do. Every trio requires a stuck-up genius after all and dodges Hanabi's attempt to hit her. Moegi asks quietly if Hanabi would prefer that they don't even if it was untrue. Hanabi doesn't answer that.
4. She would never admit it but Hanabi is jealous of Matsuri's bird summons.
5. Moegi's grandmother and Hanabi's father do not approve of Matsuri. It's okay because she isn't particularly fond of them either.
6. If asked who was the worst prankster she knew, Moegi's answer would not be Naruto or Konohamaru. It wouldn't even be Iruka. (And yes, she has realized that her former teacher was a notorious mischief-maker. It takes one to know one, after all.) The biggest trouble-makers she has ever met are the unholy pair of Hanabi and Matsuri.
7. One day, Matsuri swears, she will tie Moegi up and cut her hair so that she can never put it in those pigtails again. Hanabi would probably help her if she did.
8. When Hanabi returns from the training trip with her father to find Konoha in ruins, her first thought is that she needs to find Matsuri and Moegi.
9. Moegi doesn't use her clan name and not even her teammates know why. Hanabi thinks she understands a bit though and envies her for it.
10. Matsuri becomes Shizune's apprentice at fourteen. Six months later, everyone knows that her preferred method of revenge is poison. In a completely unrelated matter, Hanabi has immunity to most of the common milder poisons by the time she's sixteen.
11. Matsuri and Moegi watch Hanabi chase Konohamaru for years and laugh to themselves when he finally realises that she's been serious all along.
12. For all of three months, Matsuri has the most massive crush on Neji and insists on training in the Hyuuga compound every two days. It ends when she sees him with his teammate one day. Hanabi finds her later and doesn't say anything even as she puts her arms around her awkwardly.
13. Hanabi and Matsuri notice that Udon likes Moegi long before she does. They're also responsible for the complete ruin of Moegi and Udon's first date. Moegi's revenge was swift and merciless.
No one has managed to figure out what exactly she did to them, only that she really does take after her grandmother more than is healthy or safe for the people around her.
14. Matsuri has only ever met the Matsuri of Suna once. It was the Chunin Exams when she was fourteen and the other eighteen. She thinks that Suna girl's nice even if she's a bit soft sometimes. The other Matsuri sees her as a lot like Sari, her best friend.
15. The boys of their generation know that whenever they spot them in a huddle, especially if they're giggling, there will be trouble.
16. Moegi spends two months going through nearly every kunoichi in Konoha before Anko takes her on as a student.
17. Surprisingly, Moegi is the first to go into ANBU. She barely lasts two years in the service before retiring abruptly after a brutal mission gone wrong that left her the only survivor of her squad.
18. Hanabi gets to jounin before the others. Her genin are not the cutest things she's ever seen and in fact are rather annoying brats but she warms up to them eventually.
19. Matsuri makes a name for herself first though. It's given to her by a squad of Kusa-nin she nearly destroys on her own. They call her the Dark Hawk of Konoha. She finds it irritating but it sticks all the same.
20. When they're older with children of their own, they still find the time to get together once a week and chat about inconsequential things like whose child will make chunin first. (It's Moegi's eldest son in the end.)
The Neji/Matsuri thing was inspired by a conversation with freshpaint.