The Golden Pikpik Carrot is a special kind of pik pik carrot. This kind of Pik Pik carrot first appeared in the Nintendo GameCube game known as Pikmin 2. In the game, Hocotate Freight assigns their new recruit Louie to ship a large load of these carrots on an allegedly safe shipping route. When Louie returns to the company (After eating the carrots) he tells the President that he was attacked by a "Ravenous Space Bunny" who ate all the carrots. This plunges the company into a 10,100 poko debt with the "All Devouring Black-Hole Loan Sharks" company.
Louie's Dark Secret
If you get a perfect on every challenge level, you will unlock the video Louie's Dark Secret. A perfect means that you beat the level without losing any Pikmin. The video shows that Louie actually ate the golden pik pik carrots, not a Space Bunny.