Filler and differences from the manga

Filler and differences from the manga

Some of the series' main heroes and villains

Planet Namek

 Filler is used to pad out the series for many reasons; in the case of Dragon Ball Z, more often than not, it was because the anime was running alongside the manga, and there was no way for the anime to run ahead of the manga (since Toriyama was still writing it, at the same time).

Frieza Saga

The company behind the anime, Toei Animation, would occasionally make up their own side stories to either further explain things, or simply to extend the series. Filler doesn't come only in the form of side stories, though; sometimes it is as simple as adding some extra attacks into a fight. One of the more infamous examples of filler is the Frieza Saga. After Frieza had set the Planet Namek to blow up in five minutes, the final fight with Frieza still lasted well over five episodes, much less five minutes, although this can be attributed to the fact that Namek simply took longer to explode than Frieza expected. Also, there were many numerous filler scenes that took place while the battle with Frieza was in motion, which accounts for much of the footage during the planet's explosion.
As the anime series was forced to expand 12 pages of manga text into 25 minutes of animation footage, these changes were introduced to kill time or to allow the (anime) writers to explore some other aspect of the series' universe. The Other World Tournament between the Cell Games Saga and the Majin Buu Saga, and the Garlic Jr. Saga (Garlic Jr.'s return from the Dragon Ball Z: Dead Zone movie) between the Frieza Saga and Trunks Saga are both good examples of this.
Besides having filler scenes and episodes, there are many changes from the original manga. Among them are the following:

DBZ - The History of Trunk

Kamehameha!

• When Tien Shinhan loses his arm while fighting Nappa, his arm becomes a stump with only a small amount of blood seen. In the manga, the scene is much more gory.
• In the manga, Frieza kills Cargo, but in the anime Dodoria kills him.
• In the original manga, Appule finds all the Namekians in the village attacked by Vegeta dead and tells Frieza, who just tells him to call the Ginyu Force. In the anime, the soldier is changed to another soldier referred to as "Orlen" (in the closed captioning for the Ocean Dub VHS 
• tapes; it is unclear if this is canonical however) who is killed by Frieza when he tells that he killed the last survivor of the village without asking him where Vegeta was.
• In the manga, after Frieza survives Goku's Spirit Bomb, he immediately strikes down Piccolo with his Death Beam technique, but in the anime, he fires his beam at Goku, only for Piccolo to jump in the way and get struck down by the beam anyway.
• In the manga, Frieza's full power was still never a match for Goku's Super Saiyan form, but in the anime, Frieza appears to have the upper hand for a short time before he begins to tire.
• In the anime, when Vegeta is brought back to life on Planet Namek, he manages to witness some of the battle between Goku and Frieza, as well as Goku's Super Saiyan form, before being teleported to Earth by the Namekian Dragon Balls. In the manga, he is teleported to Earth almost immediately after being revived and does not get a chance to see Goku as a Super Saiyan for the first time until Goku returns to Earth himself later on.
• The anime has two significant filler portions: the Garlic Jr. Saga and the Other World Tournament segment of the Great Saiyaman Saga.
• When Dr. Gero first appears in the series (as Android 20), he grabs a man by the neck and tears him through the roof of a car. In the original manga, he crushes the man's neck afterwards, tearing his head off.
• In the manga, when Goku fully recovers from the Heart Virus, Chi-Chi finds him simply looking out the window of the bedroom he was resting in at Kame House. In the anime, however, Chi-Chi finds him outside the house, firing several Kamehameha blasts across the ocean.
• During Gohan and Cell's Beam Struggle in the anime, Piccolo, Krillin, Tien, and Yamcha unsuccessfully try to distract Cell before Vegeta succeeds in doing so, whereas in the manga, they all simply observe the struggle and Vegeta is the only one to attack Cell from behind.
• Though the flashback of Future Trunks and Future Gohan fighting Androids 17 and 18 is present in both the anime and the manga, there are notable discrepancies between the flashback and the scene depicted in the TV special Dragon Ball Z: The History of Trunks. In the special, Gohan had not lost his arm yet at beginning of the story, Trunks had not yet achieved his Super Saiyan form too, and there was rain in the scene in question.
• When Vegito fights Super Buu (with Gohan absorbed) in the manga, Vegito immediately transforms into his Super Saiyan form. In the anime, Vegito fought in his base form for a while before becoming a Super Saiyan.
• When Goku begins his battle against Kid Buu in the manga, he transforms immediately into his Super Saiyan 3 form. In the anime, however, Goku starts the battle as a Super Saiyan 2, and manages to hold his own against Kid Buu for a while before ascending to Super Saiyan 3.
• In the manga, many characters have a different number of fingers on their hands; such as Piccolo (3 fingers and a thumb), Dodoria (3 thumb-like fingers), and Imperfect form Cell (two long fingers and a long thumb). In the anime, everybody has human-like hands with 4 fingers and a thumb. 

Super Saiyan 3

Goku Ascension Levels

Gohan Versus Mini-Cell