It is advised that you read this section if you are not familiar with the Dragon Ball world. All of my reviews of DBZ movies contain these characters, so it is best that you familiarize yourself with them.
Goku - The main character of Dragon Ball and Dragon Ball Z. In the Dragon Ball series, Goku is a young child with a tail who is discovered by Bulma in her search for the seven Dragon Balls. He was told by his grandfather Gohan that he was found in the woods as a baby. Gohan died and left Goku on his own. However, Goku is unusally strong and was taught martial arts by his grandfather. He was later trained by Master Roshi (Kamesennin, the Turtle Hermit).
In Dragon Ball Z it is discovered that he was actually an alien from the planet Vegita and his name is Kakarot. Throughout most of the series he remains the strongest character of all because he is constantly training. He is also the most virtuous character, being completely pure of heart, but sometimes a bit naive.
Bulma - (Buruma)Bulma is the one who discovered Goku and started the whole search for the Dragon Balls. Bulma is the daughter of the president of the Capsule Corporation, which manufactures all sorts of gadgets. Bulma invented the Dragon Radar, which locates Dragon Balls. She is a rather irritating character, there mostly for comic relief, but aiding the characters every now and then.
Gohan - Gohan is Goku's son, named after Goku's grandfather. Gohan is introduced in the first episode of Dragon Ball Z as a small child who has been pampered by his mother Chi Chi and ignorant of martial arts, as per his mother's wishes. He starts off as a whiny brat. However, when Piccolo takes him under his wing to train him to fight against the impending attack of the Saiyins Vegeta and Napa, his attitude changes and he begins to be much tougher and less whiny. He becomes very close to Piccolo, being almost a son to the Namek man.
Piccolo - An alien from Namek, Piccolo starts off as Goku's enemy in the Dragon Ball series. Avenging his the death of his father, Piccolo Daimou, he tries to defeat Goku at every turn.
In the Dragon Ball Z series, Piccolo is forced to side with Goku in order to defeat Raditz, Goku's brother who came to get Goku to join him and the other Saiyans in conquering and selling planets. Once Raditz is defeated and Piccolo learns of the coming of the other Saiyans, he forcefully takes Gohan, who showed signs of being extremely powerful, in order to train him. During the course of training Gohan, Piccolo grows fond of the boy and even dies protecting him from Napa, one of the Saiyans (he is later brought back to life using the Dragon Balls from Namek).
Kami - Piccolo's other half, the "good" half. Kami is the guardian of the Earth. He is from the planet Namek. He separated himself from the evil inside of him, giving birth to Piccolo Daimou (Piccolo's father). Since Kami and Piccolo are connected, whenever one feels pain, the other feels it. The same goes for death; when one dies, the other dies also. When Kami dies, the Dragon Balls disappear.
Krillin - (Kuririn) Krillin is Goku's best friend. He is a short bald figure with no nose (yet he is still considered human!) and six dots on his forehead, the symbol of a temple he used to belong to. He was trained by Master Roshi along with Goku.
While not being the strongest character or even the bravest, he is usually the most determined because of his love for Goku and the rest of the team. And he has one of the coolest moves...the Destructo Disk!
Master Roshi - (Kamesennin, the "Turtle Hermit") Master Roshi was once one of the strongest and fiercest master of martial arts. However, as most people do, he got old. He lives in the Kame House ("Turtle House") on a small island in the middle of the sea. He is a rather nice old man. However, in the original Japanese versions, he is a bit of a pervert.
Seeing the power the Goku possessed as a child, he trained the boy, teaching him the secrets of hte Kamesennin style of martial arts, including the powerful Kame-Hame-Ha ("Destructive Wave of the Turtle").
Although old, Roshi can still hold his own in a batttle.
Vegita - Prince of the Saiyans, one of the very few surviving ones, a race of space pirates who find planets, elminate all life on them, and then sell them. He was first introduced when he came to Earth with his partner Napa, searching for the Dragon Balls so he could wish for immortality. Goku defeated him and thought that that would be the end of him. However, Vegita is one of the most prideful and stubborn characters in DBZ. He goes to Namek looking for Dragon Balls but is forced to join with Gohan and Krillin in the fight against Frieza. Later on he joins the team with Goku and the rest because he wants to train so he can eventually be stronger than Goku.
ADDITIONAL CHARACTERS
The Ox King - The Ox King is the father of Chi Chi. When he is first introduced, he is a fiercesome and angry man who attacked anyone who came near him. When Goku helped The Ox King get his home back (in the process destroying it however), The Ox King becomes his friend. He was trained by Master Roshi and was training partners with Gohan, Goku's grandfather.
Chi Chi - Quite possibly one of the most annoying characters ever. Chi Chi is Goku's wife. She constantly nags Goku for not being responsible (which he shrugs off most of the time). She is also extremely overprotective with Gohan and doesn't like him training to fight, but instead encourages him to study all the time. Her intentions are good, but she's still irritating.
Oolong - Originally known as Oolong the Terrible. Oolong is a shapeshifting pig who can only hold any given shape for 5 minutes. When Goku first found him, he was terrorizing a small town in order to take all the women for himself. Goku stops him and forces him to come along. He is a friend to the team later on, but plays no big roles in any fights or anything.
Yamcha - (Yamucha) He was once known as the desert bandit. He was an enemy of Goku's in the Dragon Ball series, but eventually comes to be Goku's friend. He is also Bulma's boyfriend for a while.
Tien - (Tienshinhan) A martial artist with three eyes. He was also Goku's enemy for while but eventually joins Goku on the side of good. His signature move is the Solar Flare, an attack that blinds his enemies.
Chaozu - Tien's best friend. He is a little guy, shorter than Krillin, and he looks kind of like a clown. He is telepathic.