Piccolo's whole life story is rather complicated...especially dealing with the fact that he's made up of several people. O-o
On the planet Namek, raging storms were killing off the Namek-jin's plants and causing your usual total destruction. One Namek, Kattattsu (is that spelled right!?), sent his son away in a spaceship. The son's name was Piccolo.
The ship landed on Earth and sooner or later Piccolo becomes the apprentice to the current Kami. Sidenote: in the first DBZ movie and in the Garlic Saga right after the Frieza saga, it is said that Garlic Jr.'s father competed with Piccolo for title and lost. If you wanna find out more about this, I suggest you watch the movie, as the anime version SUCKS and was never in the manga.
When Piccolo finally became Kami, he began to feel a great pain. Because a Kami must be pure and have no evil inside of him, Piccolo purged the evil away from himself. The evil became Piccolo Daimou, the demon king. Kami couldn't kill Daimou, on account they were connected. If Kami killed Daimou, Kami would die and vice versa. Daimou was finally sealed up by Roshi's teacher in a jar but the technique killed Roshi's master. Years and years later, Daimou was freed by Emperor Pilaf and set loose on Earth.
Daimou was later killed by Son Goku, but just as he died, he spit out an egg that flew off into the distance. All of Daimou's experience and memories were put into the baby inside so that Daimou could have his revenge even after his death. The baby hatched and called himself "Ma Jr." This is the Piccolo we all know.
Piccolo (Ma Jr., whatever!!) appeared at the Tenkaichi Boudokai five years later (???) to kill Son Goku, rule the world, blah blah blah. He did all sorts o' stuff, such as sealing Kami in a bottle, blowing up the stadium, and fighting Goku. He lost, but Goku spared him. He took off running, swearing he would someday kill Goku.
DBZ begins after this. Raditz kidnaps Gohan, Goku and Piccolo team up to kill Raditz, Goku dies, and Piccolo kidnaps Gohan too!! But this last thing is good, on account Piccolo has seen the amazing powers that lie within the tyke and decided to train him. A startling reaction took over Piccolo though: he was actually, kinda-sorta NICE. In fact, he became so good that he sacrificed his own life to save Gohan, after which he gave a very nice and sendimental speech, crying!!!! AWWWWWWWWWWWWWW!!
You don't see Piccolo for a while (DAMN!), but he reappears to save Goku's butt from Frieza. On the way there, he meets up with super-cool Namek-jin Nail. The two fuse and Piccolo is actually the strongest guy around for a while. ^^ And after the Frieza Saga, he fuses with Kami to fight Cell, finally becoming the original Piccolo again. Confusing, neh? @_@
He lives up at Kami's Tower with Dende and Mr. Popo as a sort-of teacher and plays his biggest role yet in the Buu Saga by training and looking after Goten and Trunks.
BTW...DON'T WATCH GT, as it is evil and Piccolo dies. Yes,you heard me, dies. (Oh my GOD, GT killed Piccolo! Those bastards!) Then he kinda acts as a police officer by keeping all the guys in Hell from getting out of line.
Piccolo started out as a cool "Get-outta-my-way" villain and that was strangely cool, making it hard to hate him like we do so many other villains *coughBuucough*. After being stuck in a desert with the brat--I mean, Gohan, he becomes more kind but still has a "don't-make-me-kill-you" attitude, which only boosted him in my liking of him. And at the very end of DBZ, I think Piccolo is at his best, having fused with Kami and making him more philosophical than Scrooge. That, and may I say that there is nothing more funny than Piccolo trying to be serious when he's NOT. ^^
