A stronger variation of the regular Oozaru, the Golden Oozaru is seen only in the Dragonball GT series. A Saiyan can transform into a Golden Oozaru while looking at the moon just in case they have previously transformed into a Super Saiyan.
In Dragonball Z, Vegeta, upon realizing that Kakarot might be the first Super Saiyan in a thousand years in the Namek Saga, mentioned that the first Super Saiyan maintained his transformation only in his Oozaru form. So it can also be assumed that Golden Oozaru is merely a Saiyan transformed into a Super Saiyan in his/her Oozaru state, as golden hair (or fur) is a Super Saiyan characteristic (with the exception of Super Saiyan 4).
This transformation was first seen when Kakarot, after being badly beaten by Baby Vegeta, looked at the Earth from the new Planet Tuffle. Initially going berserk, he eventually regains control, and transforms into a Super Saiyan 4. Vegeta in the Shadow Dragon Saga, despite not having a tail, transforms into a Golden Oozaru by being exposed to amplified streams of Blutz wave emmisions produced by Bulma's Blutz Wave Generator. Vegeta, who has had the ability to retain rational (and even speech) while in the Oozaru form since and most likely before his first arrival on Earth in Dragonball Z, was able to quickly progress through the transformation from Golden Oozaru into Super Saiyan 4.
As a result of being a mixture between the regular Oozaru, and Super Saiyan transformations, this Golden Oozaru possesses much more power than either of these forms individually. In this form, a Saiyan can now launch a massive, deadly ki blast from their mouths, capable of wiping out everything in their nearby surroundings.
The Golden Oozaru retains all the characteristics of a normal Oozaru, apart from the fact that it has golden fur, instead of brown. This is presumably due to the Golden Oozaru being a "Super saiyan" form of a normal, brown, Oozaru.
 Characters that used this transformation:
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