(as far as DBZ is concerned though i'm gettng a little annoyed with the majin buu saga, which prior to recently had been a favorite with me, but i'm getting sick of watching them try to fight him the same way over and over to no avail because DUH, he always re-sticks-together. saiyans aren't so quick on the uptake i guess) - email from a friend
The last great enemy in Dragonball Z. Majin Buu is refered as a "magical device of destruction", which pretty well sums it up. He is a giant pink blob, seemingly very stupid, but also incredibly powerful. People have described him as looking like a fat baker, because he wears what look like yellow oven mitts on his hands. His only enjoyments are beating the living daylights out of anyone who bothers him, and, for a taste of the bizarre, he can also turn people into food, and eat them (for example, he turns an entire city full of people into gumballs, and eats them right up). He also, for all intents and purposes, cannot be harmed; attacks just bounce off him and he quickly re-forms into his previous shape.
Millions of years ago, Majin Buu was created by the wizard Bibidi, who used Buu's incredible power to destroy entire galaxies for his own amusement. At some point, Buu killed 3 of the 5 Kaioshin, the most powerful gods in the universe, and absorbed another one of them, gaining his powers. Each Kaioshin was said to be 1000 times more powerful than Freeza. Bibidi was eventually killed by the last surviving Kaioshin, who is refered to in the English translations as the Supreme Kai. Buu ended up being locked into a giant sphere and buried deep underground on the Earth.
Fast forward a few million years. Babidi, Bibidi's son (get it: Bibidi, Babidi, Buu?) releases Majin Buu from his prison. Buu easily defeats Gohan and the Supreme Kai, and then Vegeta challenges him to a fight. Vegeta is almost defeated, but Trunks and Goten save him. Then, Vegeta realizes that he cannot win the fight unless extreme measures are taken. He essentially releases all of his energy at once, blowing Majin Buu and himself completely away.
Of course, that's not the end of the story (and I even left quite a bit out in the above description), but that should do it for now. Vegeta committing suicide in order to destroy Majin Buu is the last epsiode of Dragonball Z that's been shown in the US at this point.
And now, the conclusion (January 12, 2003)
I'll take this up where boi_toi's writeup (below) leaves off.
Buu basically kills everyone on the lookout, except Dende, who escapes and seemingly ends up wandering around the wilderness like some old-school Christian prophet. Then Buu totally destroys the lookout. Man, Mr. Popo is going to be fucking pissed about that.
Gotenks and Buu fight for a while, but it starts to become obvious that Buu is way more powerful, and that Buu is just bored. Fortunately, while all this has been going on, Gohan has been training in the otherworld with some super powerful gods-whose-exact-status-is-not-explained-in-the-US-releases. Anyway, skipping a lot of rather boring stuff, Gohan ends up being more powerful than anyone. Woot.
Gohan of course shows up in the nick of time and challenges Buu. For once, someone actually manages to beat him up pretty good, but Buu actually does something intelligent for once, and absorbs both Picollo and Gotenks, giving him the upper hand once again. He and Gohan fight for a while, though Gohan gets beat up rather badly, and subsequently eaten.
Also in the meantime, Goku is a) able to come back to life, and b) given some magic earrings which can fuse two people together for life. He comes back to Earth planning on fusing with Gohan, but Gohan is busy getting digested by Buu so that doesn't really work out well. Of course there is another deus ex machina waiting to help our heros out, in that Vegeta returns to life just a few miles from where Goku is. That's good because Buu is looking to kick some more ass, so Goku promptly heads over and convinces Vegeta to fuse with him. Vegeta is not a terribly big fan of Goku (or teamwork), so it takes a bit of time.
So then, Goku and Vegeta fuse into Gogeta (or is that Vegeto?). Anyway, he's really, really powerful, and the nice thing is, he doesn't fuck around like Gotenks did. He quickly and efficiently beats up Buu so bad that Buu's regenerative capabilities actually fail. Buu is not pleased, and tries to crack the universe into pieces. A quick punch in the nose and a dip in the ocean calms Buu down, however.
Gogeta gets turned into candy, and continues to battle on! It's the amazing fighting candy! Eventually the food effect turns off and he returns to his normal arrogant self. Then he gets eaten for real, which (for some reason they don't really explain) makes him return back to regular old Goku and Vegeta. But now they're small and inside Buu (what's that one movie called? You know what I mean). They spend some time in Buu's innards, checking out his colon and so on, and eventually find and release Gohan, Goten, Trunks, and a bunch of other people. While they're in there (wherever, exactly, there is), Vegeta finds good 'ol fat Buu inside, and shoots him free. Then they all escape out of Buu's ear or something.
Buu, of course, undergoes yet another transformation. Who would have thought? And instead of getting less powerful, he gets even more powerful. Again, suprise suprise. Well, that's all for now.
Toriyama really should have ended DBZ after Frieza.