Nimbus cloud
The Nimbus Cloud is
essential in Dragonball. The Nimbus cloud is a small yellow cloud, that
flies fast. When it flies, it makes a sound that an old car would make.
Master Roshi was the keeper of the Nimbus Cloud, until Goku came along.
Because Goku had rescued Master Roshi's Turtle, Master Roshi decided to
give Goku his Nimbus Cloud. There was only one requirement to be able to
ride the cloud; the rider's heart must be pure. Master Roshi was now
unable to ride the Nimbus Cloud because his heart had become inpure with
all those "Dating" Magazines. Because in most of Dragonball, the
characters were not able to fly, the Nimbus Cloud provided a great means
of transportation for Goku anyway.
The Nimbus Cloud was mainly used in Dragonball. In Dragonball Z, the
main characters figured out how to fly, and the Nimbus Cloud was not as
used as much, especially near the end of DBZ. The Nimbus Cloud however
could fly fairly fast (but not as fast as most of the Z Fighters), which
is why Goten used the Nimbus Cloud to fly around.