Why did Super Buu become Kid Buu after Fat Buu was removed?

[Analytical Delusion]

I'm sure this has been the topic of discussion before, but from reading around, there doesn't seem to be a consensus in-universe explanation for why both the Skinny Buu and Kid Buu exist.

The formation of the evil Skinny Buu makes some sense. There is some precedent for fighters expelling their evil side (Kami+King Piccolo). Fat Buu gets angry, and out of the expelled smoke, we get Skinny Buu. I follow to this point.

The Skinny Buu then reflects a candy beam back at Fat Buu, and turns him into a cookie. He becomes Super Buu. This is also fine.

Flash forward to Goku and Vegeta inside of Buu. With Gohan, Piccolo, Goten, and Trunks removed, we're back at Super Buu. He tells Goku and Vegeta that the Fat Buu received special treatment, and if he's removed, that he (Super Buu) will cease to exist). He's removed, and we get (after an intermediary phase) Kid Buu, who we had not seen to that point. But why?

I think it comes down to three questions for me:

(1) What is the special treatment that Fat Buu received?

(2) What exactly *is* Fat Buu once removed?

(3) What is the difference between Skinny Buu and Kid Buu?

My preliminary answers:

1 - I believe that Super Buu (or Skinny Buu, or whatever we want to call the base), either consciously or subconsciously, had the Fat Buu set up in a way, to both sap his "Buu" power away, and to keep his intelligence/sense of reasoning intact.

2 - I think that Fat Buu, at this point, is purely the combination of the two Kaioshins he absorbed. After millions of years inside Buu, they devolved into the form we've seen.

3 - I wrote these two answers while considering Kid Buu being the original Buu, with all of his strength intact. That is to say, once Buu was removed, he was purely the original Kid Buu. On the other hand, *both* the Skinny and Fat Buus possessed some of the strength and characteristics of Kid Buu, and (rehashing my response to 1), it was only after the Fat Buu was absorbed that the Skinny Buu isolated/completely separated the Kid Buu/non-Buu elements.

Anyhow, what do you guys think? Why are these two different entities?

[theherodjl]

Good Boo was a reiteration of Dai Kaioshin in possession of a dormant South Kaioshin's power which was inaccessible until Pure Evil Boo absorbed Good Boo, afterwards Super Boo was born and quarantined Good Boo within his head until it was discovered by Goku & Vegeta then removed. Afterwards Majin Boo went through a hard reset by reverting back to Buff Boo and then shrinking to his base state of Pure Boo.
Something like that anyways.

[dbgtFO]

Fat Buu expelling his evil was not a clean break with the Kaioshin influence, thus we end up with Skinny Buu, who is Fat Buu's anger and his opposite, but still very much influenced by the Kaioshin. I theorize the case is that the Kaioshin are completely digested in Fat Buu's body, so returning him to his pure state wouldn't be possible the way Goku and Vegeta removed their friends and family from Super Buu.
After Skinny Buu absorbed Fat Buu, for some reason("he was a special case"?) all the Kaioshin influence was put in Fat Buu, allowing for a clean split between Buu and the Kaioshin influence, so removing Fat Buu would also result in the original Buu returning, as he'd have no Kaioshin influence anymore.
That's my take.

[Desassina]

My guess is as follows, this time with a few formulas and comments, so that they're easier to follow:

South Kaioshin Buu (Pure Buu + South Kaioshin). The name implies that he is the original Buu with the Kai's strength and bulkiness added to him.
Majin Buu (South Kaioshin Buu + Dai Kaioshin). He's an unpredictable result: the ferociousness of S.K. Buu was tamed by this Kai's docile nature.

Pure Evil Buu (Pure Buu + Evil). He's an entity that split with more power than his remainder, resembling Majin Buu as a distorted Pure Buu.
Innocent Buu (Majin Buu - Evil). Without his evil, he became powerless, but still the separate entity in a Buu body to empower the other.

Evil Buu (Pure Evil Buu + Innocent Buu). Pure Evil Buu would have killed Innocent Buu upon eating him, but he had a special treatment.
Evil Buu (Pure Buu + Majin Buu). Pure Evil Buu returned his evil to Innocent Buu, allowing him to become the original fat Majin Buu.

And here's the confusing part now. When Evil Buu ceased to be himself and Pure Buu took over, the latter may have tried to tap into the South Kaioshin absorption in Majin Buu, but he lost grip when he realized that it would come with Dai Kaioshin as well. He could only do that if Majin Buu was reattached, and he might as well have been, because the memories of Mr. Satan were still affecting him. For Pure Buu to have spit Majin Buu out, he must have stored the latter on a corner, without using his power. It would help us know that South Kaioshin didn't affect him in terms of personality, because Pure Buu was still himself with that absorption, when Dai Kaioshin was the one to prevent his influence from getting unused with a trap.