Every Ball Race map has an achievement called ‘Nimbus Hidden Treasure, Paradise Hidden Treasure, etc.’. All of these achievements need you to collect 3 Golden Melons on the specific maps. So what even are Golden Melons?
The exact description : Discovered the 3 golden melons in map_name_here.
I can confirm that they are not in game right now, since achievements isn’t in the game YET
achievements are the next thing they have on the list of updates, so expect it to be soon