Gold Goomba

Gold Goombas are golden variants of Goombas that appeared in Super Mario RPG: Legend of the Seven Stars and some Mario Party games. They are basically the same as Goombas, except they are only found in minigames and are worth three points while their brown counterpart is worth one.

Super Mario RPG: Legend of the Seven Stars
In Super Mario RPG: Legend of the Seven Stars, Gold Goombas appeared in the Goomba Thumping minigame found in the Pipe Vault. They are worth three points, compared to Goombas which are worth one and Spikeys which cause Mario to lose a point. However, they are both rarer and faster than regular Goombas, only appearing for a short amount of time during the course of the minigame.

Mario Party series
Gold Goombas make their first Mario Party appearance in Mario Party 6, where they appear in the minigame Trap Ease Artist, being worth three points, as in Super Mario RPG. In Mario Party 7, Golden Goombas appeared in Royal Rumpus. They also appear in the Mario Party DS minigame "Goomba Wrangler", where they are worth three points, while regular Goombas only give one point.

New Super Mario Bros. 2
Gold Goombas also appear in New Super Mario Bros. 2. However, they're simply regular Goombas after Mario or Luigi touch a Gold Ring. The player will get 5 coins for each enemy defeated. The same applies to other gold enemies.

Trivia

 * In Super Mario Advance 2: Super Mario World, Goombas turn gold and wear glasses after finding all 96 exits.