The Gold Fuzzy, as the name states, is a Fuzzy that is golden in color.
The Gold Fuzzy is first seen after Mario gets both the Sun Stone and Moon Stone and tries to leave Shhwonk Fortress. The Gold Fuzzy sees Mario as a tresspasser and enguages him in battle. However, he was soon defeated and he and his Fuzzy Horde leave.
In battle, the Gold Fuzzy can attack by simply jumping at Mario or his partner. It should be noted that the Gold Fuzzy is the only Fuzzy in the series to not drain HP when attacking. The Gold Fuzzy can also summon a Fuzzy Horde that attacks with Fuzzies leaping at their target (they do not drain HP as well).
The best tactic to defeating the Gold Fuzzy is to focus on the Gold Fuzzy itself. Do not bother targeting the Fuzzy Horde as they have double the amount of HP the Gold Fuzzy does (20 HP) and they are defeated anyway after the Gold Fuzzy is defeated. The Gold Fuzzy and the Fuzzy Horde's attacks are simple to guard against making this battle rather easy.