Dragon BallJust as Piccolo Daimao was dying from a gaping hole in the chest, he coughed up an egg and spat it into the sky. Son Goku, however, did not notice this. Ma Junior is first seen as a little child roaming the woods after "hatching." He turned evil due to the loss of his father, and is jealous of a family he sees through the window. Even at this young age, Ma Junior possesses many of his father's or past life's (depending on how you look at it) powers.
Years later, a teenage Piccolo makes as a return at the Tenkachi Budokai, planning on fighting Goku in it. In the finals, both Goku and Piccolo end up in battle. As they fight, Goku finds himself in the hardest battle he has ever been in up to that point, however, Goku still tries to play by tournament rules, which handicaps him. By the end of the fight, Goku defeats Piccolo, having managed to knock Piccolo out of the ring (and leaves him unconscious in the process). Goku does not kill him and, in fact wants him to be his rival, so that Goku would have the motivation to keep getting stronger. Piccolo then leaves and went on to begin his training in five years before Goku and Chi-Chi depart their friends and got married.
Dragon Ball Z
After five years of training after his defeat to Goku, Piccolo notices a strong power on Earth, much more powerful than Goku. He goes to the source to find an alien named Raditz. Piccolo tries to defeat Raditz but fails. After Goku's son gets kidnapped by Raditz, Piccolo proposes that they work together, since alone they are both not match.
They go off to find the alien, and fight him. After awhile, it becomes apparent they are no match, so Piccolo tells Goku to hold Raditz off for five minutes, so he can charge his new attack, the Makankosappo (Special Beam Cannon). Piccolo fires the attack, but Raditz dodges last second. In desperation, Goku holds Raditz from behind, and Piccolo once again fires his Makankosappo, killing them both. Before Raditz dies, he announces that two stronger Saiyans will arrive on Earth in one year.
To prepare for the next fight, Piccolo takes Goku's offspring Son Gohan to train him; at first this is his idea of revenge against Goku. But overtime, he starts to grow attached to Gohan, and helps him stay alive in the wilderness. After one year, Piccolo believes Gohan to have become stronger then him, but while battling Nappa, Gohan freezes in fear, and Piccolo jumps in front of Nappa's Bomber DX in order to save Gohan, and, just before dying, said was his only friend.
Piccolo receives training from Kaio in the afterlife. He is eventually wished back to life and once Piccolo reaches Namek the home of his people, he fuses with Nail, a powerful Namekian warrior. Nail eventually fades away; shortly, this increases Piccolo's strength, dramatically rising his power level over one million. Piccolo defeats second form Freeza, but is defeated by third form Freeza before being saved by his best friend Gohan. Piccolo, Gohan, Vegeta, and Kuririn all try to damage Freeza in his final form, before Goku eventually does it in Super Saiyan form.