In this volume, Boo begins to gain some independence from Babidi, Son Goku makes a show of the three forms of Super Saiyan, Son Gohan trains with the Old Kai, Mr. Satan becomes useful, and the little boys practice Fusion.
Looking at a list of the anime episodes, it appears Toei really extended a lot of the content here. In the span of about one full volume of manga, Fat Boo ceases to be a grave threat and is pacified by Mr. Satan. Some human goons are seen taking advantage of Boo's destruction of 80% of the world's population to live out fantasies of committing murder themselves, and somehow gain the inspiration to try to kill Boo. They shoot the dog (Bee) and Mr. Satan, but not fatally enough that Boo can't heal them. Despite restoring his new friends, Boo cannot contain the rage boiling inside him, and an Evil Boo is born from the steam-holes in Boo's head (similar to how Fat Boo came from the steam of his egg). Fat Boo only spends like three chapters with Satan, and the murderer guys are only in the last chapter, with maybe a few panels in the one before that (I already forgot, after reading it some hours ago...). Boo's character development thus occurs pretty fast, not unlike the high speed by which Vegeta became a family man after (ab)using Babidi's power to become an SS2. So, technically, the pacing of the writing is maybe... not so hot, BUT (and this is probably mainly because of Nostalgia...) I was moved.
As I've done a few times before, it's time for me to approach questions of lore consistency with my own "headcanon." As we will learn in the future, Boo originally began in the form Americans commonly refer to as "Kid Boo," otherwise known as the "Pure Boo." This Boo kills two Kaioshin before deciding to absorb two more, one a muscular Kai who turns Boo into a ripped 'roid-rager, and the other a docile chubby Dai-Kaioshin whose gentleness is able to force Boo into his Fat form (which, incidentally, allows Bibidi to better control him). In this volume, Fat Boo is able to eject his anger and evil power into a separate form, who does not resemble Pure Boo. Thus, my headcanon is that Evil Boo still has too much of Dai-Kaioshin's heart within him (signified by his cape, I guess). Somehow, the Evil Boo is able to eat the Fat Boo (whose appearance hasn't changed), and gain a form not unlike his Pure state (but taller... for some reason...). My guess is that Evil Boo's victory over Innocent Boo allows him to better suppress the Dai-Kaioshin's goodwill, sidestepping the "need" to resemble the Kai with his cape. Why is he muscular? Uh... I guess just because he wants to fight Goten and Trunks, so he keeps himself in a more battle-appropriate form? Kibitoshin later mentions that Boo is weakened by the hearts of the Kais within him, which I suppose works well enough to explain why Super Boo has the physique of a fighter rather than the juvenile appearance of his raw form. And... you know... he's "Super," so... that plays in as well.
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*Babidi: "Oops! I think it's more messy than before!"
*exploding the Budokai snitch's head
*Son Gohan embarrassed by the Kibito clothes, despite being proud of his Saiyaman suit
*Gohan: "Pull it out, huh? I feel like I've heard this somewhere before..." I assume Toriyama's just making a King Arthur reference, but I choose to interpret it as a lewd joke.
*Son Goku, to the kids: "Stop crying! We don't have time for that! If you're sad, learn this new technique as fast as you can... then, you can avenge them! Got that?!"
*Kibito, after making a fool of himself being unable to lift the Z-Sword: "Indeed, it's a little heavy..."
*Boo goofing off behind Babidi's telepathic broadcasts
*Boo, to Babidi: "Seal me... and he kill you."
*Goku: "OK, then... I have to go beyond the surpassed Super Saiyan's level!" As we've meme'd from Funimation's dub: "And this... is to go further beyond!"
*Goku: "It's nothing. Don't worry about it." Vaguely waving the idea of the Dragon Radar away from Boo's attention.
*Goku: "The one that once again surpassed its predecessor..."
*Super Saiyan 3's missing eyebrows and protruding brow ridge, as well as the absurdly long hair. Pretty sure Toriyama was taking the piss with this design, but all of us kids loved it!
*Goku grabbing Boo by the antenna and bopping him around
*Boo copying the Kamehame-Ha
*iconic shot of Boo with hands on hips in Chapter 475
*Boo: "Hey! Why you changing back! It's fun fighting with you. I want to fight more!"
*Boo, after grabbing Babidi's face: "You can't talk now, huh? Babidi can't say spell to seal Boo away!"
**Boo exploding Babidi's head with a punch
*Boo turning his face into that of a male model in order to prank a random girl
*Goku: "It's because I used the Super Saiyan 3 earlier... It's something you can only use in the other world. If you use it in a place where time flows, like Earth, it uses up way too much energy and exhausts you completely..." Something like foreshadowing for the Gotenks vs. Super Boo and Goku vs. Pure Boo fights.
*Goku: "It's just that I'm no longer part of this world. It's not my turn to save the world anymore. I have to step back and leave this fight to the young ones... And you never know when an even stronger opponent will appear. It's a terrible risk we're taking... but I think these two little super prodigies are good enough to let them try..." God damn, would I kill for Goten and Trunks to have further relevance in the story. And Pan and Oob. But, at most, Trunks and Pan accompany Goku in the beginning of GT, and after Goku gets SS4 no one else matters (aside from using Vegeta as a battery for Fusion).
*Goku, to Piccolo: "I think the worst for him about being dead is that he isn't able to see you anymore." In reference to the (mistaken) belief that Gohan is dead.
*Trunks, about Fusion poses: "Is it just me... or was that really lame?" But all the practice goes to his and Goten's heads, and Gotenks will be even zanier than the dance that creates him...!
*Piccolo: "You... you said you wanted to try this with Vegeta but... I seriously doubt that he would have agreed to this if he was still alive now..." Fast-forward to 2018 and the Dragon Ball Super: Broly movie...!
*Boo's house is made of humans he transformed into clay
*Videl: "Uhm... I... I think that Gohan is still alive!" Just as Bulma earlier sensed Vegeta's death, there's some kind of connection between human wombs and Saiyan energy....
*Goten wanting a hug before Goku leaves, paralleling Vegeta hugging Trunks before exploding
*Goku: "See you guys!! Let's meet again when you die!!"
**Kuririn: "That... that rascal... He had to say something that hopeless, did he?"
*Boo turning the old lady into milk for the blind kid, setting up his face turn later on
*I forgot it was Kaioshin's idea to throw the "katchin" at the Z-Sword...!
*Old Kai has pale white skin in the Full Color manga, unlike the purple of the anime (so his manga color is different from Kaioshin's, where the anime gives them similar skintone)
*Goku, to Old Kai: "If you tell me, I'll give you a dirty magazine!"
**"And how about touching a girl's chest and butt?"
*Goku, to Gohan: "Since I can't go back to Earth... you'll have to, you know, introduce him to your girlfriend."
*Goku, to Gohan, after Old Kai agrees to grope Bulma: "See? A little flirting can save the universe."
**Gohan: "But that's sexual harassment... Even if the world is saved... I'll be doomed for sure."
*Old Kai: "I always hoped that a Kaioshin would release me from that prison. Instead it's an earthling, what's the world coming to?"
*Old Kai's goofy dance to awaken Gohan's power
*Chi-chi: "Goten and Trunks... Probably Trunten or Gotenks... Neither sounds good."
*fat and emaciated Gotenks mis-Fusions. It's of course necessary for later Gogeta appearances to follow suit.
*Kuririn, about reused Fusion Dance panels: "Wait a minute! What's Toriyama trying to pull? These panels have gotta be photocopies!"
*Gotenks: Nuh-uh-uh... Do not underestimate me. This is enough to beat Boo!!" *gets his ass kicked off-panel*
*Satan: "Lay down right here [...] Yeah. It's the popular way these days." Satan and Boo invented the "planking" fad?!
*Bee the dog is introduced, giving Boo some cute moments
*Satan can actually beat up regular humans, so he's not completely weak
*Evil Boo exploding the guy
*the birth of Super Boo, who doesn't need a cape or gloves anymore
*Super Boo pulling back from attacking Satan, then flying away as if running away from the humanity born in the heart of Fat Boo (setting Satan up for further relevance in the end)
*Boo: "BRING!!! [...] The one's who'll fight me. I was promised they would fight me. I want to kill them soon. They should be here, this is the place with people with lots of power."
*Human Extinction Attack, after Boo paces around the Lookout enough to locate every remaining human's ki. The full-page panel of attack itself is very pretty in full color. Looks like fireworks. Genocidal fireworks, but still...!