Piccolo  is the reincarnation and final son of the original King Piccolo, and was born to avenge his father's death at the hands of Goku. According to Guru, Piccolo, along with Kami and King Piccolo, are part of the Ryu or Dragon Clan, who were the original creators of the Dragon Balls. After his narrow defeat against Goku, Piccolo is soon forced to form an, at first, uneasy alliance with Goku and his friends against newer, more dangerous threats. Thus, he and Goku kick off the formation of the Z Fighters. Also, out of necessity he also takes it upon himself to train Goku's young son Gohan, forming a powerful bond which ultimately redeems him when he sacrifices himself to save the child's life. After his resurrection he fully joins Goku and the others in their struggles against ever more powerful villains on Planet Namek and Earth. As the story progresses, his role shifts from warrior to mentor.

When Piccolo Jr. is introduced, he appears roughly the same as King Piccolo, but with a more solid facial structure (lacking the large cheek bones and a humanly-shaped nose), as well as slightly thinner and a bit shorter (though technically he doesn't appear as a full grown adult until Z). Piccolo Jr.'s outfit when he was small was a very similar outfit to the one King Piccolo was first seen wearing (being of the exact same color scheme in the Kanzenban covers of the original manga), and from the time he's a young adult onward he wears the same gi as King Piccolo but minus the chest symbol and the color scheme switched where his gi was dark purplish blue rather than dark pale blue, and his obi light pale blue rather than light purplish blue, and he wore a white turban and an extremely weighted cape along with it when not fighting seriously. As the series went on Piccolo Jr.'s outfit became more his own, and by the time he faced Frieza his gi lost whatever blue was in its color and gained more of a purple one, his neckline becoming more low-cut like Goku's outfit, minus Goku's own undershirt. In the manga and in many of the movies he wore a red obi rather than a sky blue one. Even though Piccolo Jr. discards his old symbol, he uses it once in the series when he made his pupil Gohan a uniform after his previous outfit was torn in a Great Ape transformation brought upon by a restored moon. In a single filler episode in the anime, Piccolo is seen wearing an old outfit of Goku's when both of them are forced to go to driving school by Goku's wife, Chi Chi.
Piccolo originally is evil much like his father. When battling Goku in the World Tournament, he shows almost no mercy and no regard for his opponent. Despite this, when he and Goku team up to battle Raditz, Piccolo does begin to show more honor during battle, even commemorating Goku on his noble sacrifice. After he trains and befriends Goku's young son Gohan, Piccolo's heart and motives quickly begin to change. During the battle with Nappa, Piccolo goes as far as to sacrifice his life to save Gohan, stating how his friendship and love had changed him forever. Upon his return during the battle with Frieza on Planet Namek and after fusing with the Namekian warrior Nail, Piccolo fights for the honor of his people and to save the innocent. Years later, during the androids and Cell arc, Piccolo still does retain a bit of ruthlessness and cockiness, but once he fuses with Kami, all traces of evil and hate disappear, and Piccolo is completely reborn as a pure soul.  Even after merging with Kami, Piccolo remains a loner, preferring to stand apart from others. He has little to say unless it involves battle, and doesn't seem to understand the concept of romance. (He often sees "mushy stuff" as disgusting).