Why isn’t the movie called Dragonball Z?
Dragonball Evolution is based on the prequel to Dragonball Z (known as Dragonball). The anime follows Goku’s adventures when he was a kid and teenager. While the movie occurs during the King Piccolo saga it still uses aspects from the first saga (sometimes referred to as the “Goku” or “Emperor Pilaf” saga, and no Emperor Pilaf is not in the film). However, DB:E isn’t that faithful to any part of the DB universe so it’s hard to tell.
The movie is based on the prequal to Dragonball Z known as Dragonball. The anime follows Goku’s adventures when he was a kid-teen. While the movie occurs during the King Piccolo sagas it still uses the aspects from all DB sagas. The sequal to the movie Dragonball is in fact rumored to be called Dragonball Z.