After rereading the Valentine's chocolate chapter of Katekyo Hitman Reborn!, I realized that Tsuna's Only Sane Man status means he is the only one capable of directing the quirky personalities he is surrounded by... In other words, he's the only one in the group who could be the boss.
In Chapter 15, it is briefly mentioned that Dr. Shamal is the one who assisted in Reborn's birth. When it is revealed that Reborn hasn't always been a baby due to his status as an Arcobaleno, this fact doesn't make sense as Reborn is older than Shamal. However, Shamal is the one who erased Reborn's former identity as a hitman after he became a baby, thus assisting in the "birth" of the current Reborn.
This troper had always thought that the fact Yuni couldn't predict the end of Tsuna's final battle with Byakuran to be very convenient but then she realized that Yuni couldn't do it because she can't see past her own death. Cue Tear Jerker.
The Bianchi + Reborn relationship starts out as squicky, then something you come to accept. It stops being mentioned sometime before the Ring Scramble, and you forget about it soon enough. Then you find out that Reborn is actually an adult trapped into the form of a baby and it becomes heartwarming, in a "I'll always stand by you no matter what" sort of way.
Except... Judging by Yuni and Aria's age, the presence of an Arcobaleno way back in the Primo generation, and the fact that Reborn was a baby at least eight years ago, when Dino was being schooled in the mafia business, and you realize that Reborn has probably been in infant mode since prior to Bianchi's own birth.. So it's still just something you have to learn to accept.
As a child prodigy, Bel joined the Varia at the age of 8. His age given during the Ring Battles is 16. Given that the Cradle Incident with Xanxus happened 8 years ago, and Bel was shown in the flashback of the coup, the Ring Battles must have happened just as Xanxus got out from an 8 year entrapment. He still managed to defeat Nono and his guardians, kidnap Nono, and devise the entire scheme to take over the Vongola. Holy crap.
Not to mention Squalo, who, according to this time frame, chopped off his own left hand, defeated the Sword Emperor Tyr, and sworn eternal loyalty to Xanxus at the age of 14.
Actually, the time frame would put him at either fourteen or younger. But of course, that doesn't make it any less impressive.
How did the Vindice take down the entire Simon Family and some of the most powerful characters in the series? Because they're former Arcobaleno!
Realizing the fact that Mukuro 10 years to the future was locked up into a prison for those years and STILL kicks major ass makes his previous asskicking make a lot more sense. While others had to train rigorously to keep up with the constantly strenghtening opponents, he already WAS at that level when the series started.
It seems a bit random of Reborn to decide that the baseball-playing Yamamoto's weapon of choice should be a sword (rather than just a regular bat)- however, it's entirely likely that Reborn researched all of Tsuna's family candidates and discovered that Yamamoto's father was a former swordsman, thus deciding that his son had the potential to take up the blade again!
Reborn's early interactions with Lambo. Sure, we know how annoying Lambo is, about all that "rivalry" thing and that he's not gonna be killed even by grenades, but once we realize it's an adult hitman beating the living crap out of 5-year old kid...
Nana, Tsuna's mother, has Abusive Parent tendencies. She belittles her son when he needs her most (since he has no self-esteem), but treats him nice once he is no longer a loser?
This is actually Truth in Television, more mothers do this than people expect them too, but particularly in Latin America, mothers whose sons prefer studying or reading and other more passive hobbies over sports and well, dating, will most likely belittle their sons.
If the Ten Year Bazooka switches you now with you ten years in the future, what would happen if you were to be hit while pregnant..?
It would just switch you after you had the baby and was 10 years old, not a 10 year old baby in there or anything.
Just a minor one, but in the recent chapter when the Varia and Kokuyo Gang were looking for Fran, it shows that young Fran, just around 9-10 years old, was living with his grandmother at France. A few chapters later, Fran is with Mukuro all the way in Japan. Did they just rip such a young boy, albeit the child being a very powerful illusionist, from his family to join the mafia?
Answering to the above troper, the blunt answer is... yes! Even though Mukuro despises the Mafia, he rather chose to put the boy into a Training From Hell and ensure that he gets Fran's loyalty from this little age. And it might be a scheme to spy on the Varia, as well.
And one bit of Fridge Logic. We all know that before major battles, Leon makes clothes that provide protection against flames, what does not sounds strange, considering that Shinu Ki Dan are made inside of him as well, but why the hell do the other fighters's clothes remains intact after being hit by the flames?
Tsuna developed his X-Burner technique in the future when he realized he could use his flames for offensive attacks by blasting said flames. Didn't he realize that he could do this A LONG TIME AGO when he blasted said flame to protect Chrome and the Kokuyo Gang when the Varia's Mosca was going berserk?. Sure, it wouldn't have the sheer firepower of the X-Burner back, and it was purely a defensive move then but it would have still been a powerful move given that it stopped the Mosca's laser cannon and the bullets from a gatling gun.