The Moon is a celestial object revolving around Earth in the Dragon Ball universe just like its real life counterpart. Its significance is that it has caused some Saiyans to transform into their Great Ape form and has been destroyed two times and revived one time.
Role of the Moon in Dragon Ball seriesEdit
Prior to Dragon BallEdit
21st World TournamentEdit
22nd World TournamentEdit
Man-Wolf, a fighter in the 22nd World Martial Arts Tournament, couldn't turn back to a human because Roshi destroyed the moon. Master Roshi used a Hypnosis Technique on Man-Wolf to convince him that Krillin's head is the moon. The Hypnosis Technique worked and Man-Wolf turned back to a human.
It was not mentioned, but the moon must have been revived during Goku's training at Kami's Lookout, as Goku in the 23rd Tournament mentions that his tail was removed so that the moon could be restored. The moon is also seen later, indicating that it has been restored.
Dragon Ball ZEdit
Goku's Space pod projected the image of a moon which again made Gohan transform into a Great Ape. When Piccolo destroyed the Space pod the projector was destroyed.
Fake moon during the battle against the SaiyansEdit
This happened when Vegeta made a Power Ball that transformed him into a Great Ape. Yajirobe cut off his tail so Vegeta couldn't transform anymore. Later, Gohan transformed after looking at the Power Ball. Vegeta cuts Gohan's tail with a Destructo Disk after a short struggle, but Gohan landed on him and Vegeta retreated.
Dragon Ball GTEdit
During Dragon Ball GT, Goku was fighting for the humans of Earth in a death-lock battle with the Tuffle King's descendant, Baby, on New Planet Plant. Although, the moon was not present, Goku was able to transform into a Golden Great Ape due the reflection of Blutz Waves by the Earth. Although it was the Earth that caused the transformation, all of the people present for the battle questioned where the moon was, including a brainwashed Bulma and Baby himself, giving an elusion to the moon whereabouts.
Moons of other PlanetsEdit
Most moons or satellites of other planets have been shown when the planet was shown, and without much significance. However, the moons of Planet Vegeta and of Planet Kanassa were important, as Saiyans had used them to transform.