Mr. Buu - Plothole?

[DemonRin]

Reveboy's explanation really is the best, but if you don't want to go through and read it, here's an explanation in mathematical form.

Start with Kid Boo

Kid Boo + South and Dai Kaioshin = Fat Boo

Kid Boo = Pure Evil, Both Kaioshins = Good

Together, they make one being with both Good and Evil within it.

Over the years in isolation, The influence of The Two Kaioshins is permanently absorbed within Boo. They are no longer their own beings (As we would later see Goten, Trunks, Piccolo, and Gohan as in Boo) but are now the "Good Kaioshin" parts of Boo.

So, Fat Boo is released. Being as he has Good and Evil inside him like a normal being, he is able to make his own choices like any normal being would. Babidi tries to make him act on his bad side, but Mr. Satan wins out and makes him act on his good Side. Now, next equation.

Fat Boo (Boo + Kaioshin Influence) / Expellation of Evil = Fat Boo (1/3 Boo + 2/3 Kaioshin Influence) + Skinny Boo (2/3 Boo + 1/3 Kaioshin Influence)

Both have "Good" Kaioshin Influence within them still, but Skinny Boo has less and is therefore more of the "Evil" within Boo.
Skinny Boo overpowers Fat Boo and takes over his power and essence, but wishing to remain dominantly Evil (As evil won) he, instead, expels all the Kaioshin Influence and stores it within Fat Boo. Since the Kaioshin no longer exist as their own beings and became a "Part" of Boo, they now exist as the "Good" Part of Boo. So now, he is Kid Boo who draws personality and power from Fat Boo just the same way he would later draw power and personality from Piccolo and Gotenks, while they remained desperate beings within him. So now,

Super Boo = Kid Boo + Fat Boo
Super Gohan Boo = Kid Boo + Fat Boo + Goten + Trunks + Piccolo + Gohan (I skipped all of these steps because this part is redundant)

Son and Vegeta then remove all the parts from him, including Vegeta removing Fat Boo, now

Kid Boo = Super Boo - Goten - Trunks - Piccolo - Gohan - Fat Boo

Or "It's Magic".

[cpd12589]

I've thought about that before and I asked myself the same question how could Mr. Buu even exist. If Kibito Kai is really correct when he says he's changing back to normal then Mr. Buu can't exist because he normally wasn't 2 separate beings. But what I eventually came to was it might have something to do with Dai Kaioshin and South Kaioshin being like permanently part of him(like they can't be removed individually anymore). So Mr. Buu just represents Dai Kaioshin and South Kaioshin and Kid Buu is same as he was when Bibidi created him. At least that's what I think :/

[Juan Fra]

At first I thought the same as Kaboom, but after reading rereboy's take on the matter I guess it makes the most sense; the Piccolo and Kami analogy fits to a tee.

Though, don't break your heads over this one, Toriyama just probably pulled it out --as his usual self-- of his you-know-what.

[Coola Yagami]

Toriyama probably liked/missed the Fat Buu/Satan dynamic and felt sorry for him and thought 'oh what the the hell, I'll make Kid Buu suddenly spit out Fat Buu again. Fuck the rules, it's MY story."

[Dayspring]

I don't see Mr Boo existing when Kid Boo's around as problematic because all Boos have regenerative powers. Basically, a Boo should be able to clone itself; it just won't be as strong without the full soul. So in this case, Kid Boo is Boo's soul in a regenerated body, whereas Mr Boo is the original body being held together by Dai Kaioshin and South Kaioshin's souls. If Mr Boo were to expell one of them, he'd completely turn into the other Kaioshin, only made out pink bubblegum instead of blue humanoid.

Basically what got expelled from Fat Boo is the soul of Kid Boo's, the personality is of Buff Boo's and the body of "Gas Boo." Gas Boo needs to regenerate into a real body, but if he does, he'll become the body of Buff Boo. Since the South Kaioshin was left behind, doing so will immediately result in a transformation back into Kid Boo. So the personality intentionally makes the "Gas Boo" form a body that can maintain his personality while just having the soul of Kid Boo within it. The result is Skinny Boo.

Super Boo - Mr Boo results in Buff Boo because of this. It's clear that Boo has no control over de-assimilations, so when Mr Boo is taken out, he can't revert back to Skinny Boo; he must revert to the natural body of Buff Boo's personality. The result is Buff Boo's body, but because South Kaioshin is inside Mr Boo, Buff Boo turns back into Kid Boo.