Welcome to the Jungle

1. Theirs is the team on which all others should be modelled. At least that's what they tell their students anyway.
It was the first one to have the bell test (Homura was tied to the log). However, it's also the first team to bear that unfortunate designation, Team Seven.

2. The real reason Koharu cannot stand Tsunade is not one what most people would think of.
Shortly after she turned twenty, a bad injury forced her onto restricted duty for two months. One of the D-ranks she did during that time was babysitting a three year-old Tsunade. What exactly happened within those four hours is something she has never told anyone but led to her nicknaming Tsunade the demon child.

3. Homura and Koharu were both from civilian families.
It's not a fact people remember nowadays but in the early years of the Academy, there was an enormous difference between clan ninja and non-clan ones. Non-clan ninja rarely made it to graduation and the chance of them passing their sensei's test was ten percent at best.
They have always been very aware of those statistics and one of their lesser-known legacies was improving the chances of students with a civilian background becoming ninja. Without their changes, neither Sakura or Tenten would have made it to graduation and Lee would have been refused entry. This is not something any of them will ever realise though.

4. The last thing they do as a team is bury their sensei. It's not a grand funeral as the Second Great Shinobi War broke out two months before but it marks the end of an era in more ways than one. Hashirama's daughter has already been dead for six years and her husband for two. The Senju name is all but extinct with the only two left being Nawaki and Tsunade.
In another two years, Tsunade will be the only one when Nawaki falls to a trap.

5. Koharu is the most terrifying person her teammates and sensei know. Her apprenticeship to the genjutsu mistress, Senju Touka, was heavily contested by them much to Hashirama's amusement.
No one else can get the sort of instant obedience that she can out of them. Consequently, her pregnancy was possibly the most stressful time of their lives.

6. All of them have buried a child. For the longest time, Hiruzen thought he would have to bury two.

7. Two weeks after he became their sensei, Tobirama nearly had a nervous breakdown in his brother's office.
He finally gets his revenge sixteen years later when Hiruzen does the same thing after only a week.

8. Each of them starts a tradition. Hiruzen is killed by his rogue student, Homura becomes an orphan at a young age, Koharu loses her best student to himself and Tobirama dies for the village.
Unsurprisingly, it's Koharu who's least proud of hers.

9. They say nothing as Hiruzen's students leave one by one. Their genin are long-buried by the time Orochimaru flees anyway.

10. There are certain times of the year (anniversaries of deaths mostly) when they put aside their differences and are merely content to be old friends.

11. The massacre is almost the final nail in the coffin of their friendship. Homura and Koharu see it as necessary to preserve the Senju ideals even if they do not agree with them. Hiruzen does not and will never look at them in the same way again.

12. One thing that they can all agree on is that Danzo is not trustworthy. Homura and Koharu may think that he has the right idea occasionally but they know perfectly well that his plans are only for his own advancement.

13. All of them end up raising their orphaned grandchild. It is a far more difficult task than they remember and they delegate it to tutors as soon as they're old enough.
(The Konohamaru Corps was formed partly out of necessity.)

14. Homura may not be as talented as his teammates but in one area, he will always beat them.
(His special gift is with blackmail. He has enough dirt on most people to bury them alive.)

15. Tobirama knows that his students would do literally anything for Konoha and that's what scares him. He very nearly has to order all three to quit ANBU because of it.

16. The proudest day of their lives is the one when they become parents for the first time. Homura does it first much to the endless annoyance of his teammates as he shoves pictures of his son into their faces at every opportunity.

17. Their first impressions of each other aren't good.
Hiruzen thinks that Koharu's a bossy know-it-all and Homura a talentless idiot.
Homura can't stand either the stuck-up clan genius or the equally stuck-up girl.
Koharu wonders why she got such a useless pair of boys for teammates.
Tobirama takes one look at them squabbling and realises Konoha is doomed.

18. Three years and dozens of missions later, their views of each other have improved considerably but they still insult each other like they're still seven. For some reason, Tobirama doesn't mind. (Konoha is still standing after all.)

19. They have known six Hokages, served in three wars and outlived most of their family and friends but in the end, they are undone by a threat of their own making.

20. Team Ebisu was put together on Homura and Koharu's insistence. Perhaps their grandchildren will get it right where they could not.

They are the best team. Sixty years later and they still get along.

Yeah, lots of head-canon here. I like the idea that Moegi and Udon are Koharu and Homura's grandchildren respectively because it fits with the whole theme of parallels in Naruto.

Tsunade was a nightmare as a child, don't deny it. xD

Touka = random Senju from the third databook.

The real reason Tobirama has white hair: his students.