Pikpik carrot
Pikpik carrots are vegetables native to Captain Olimar's home planet, Hocotate. They are the sole reason Pikmin have their name, because Olimar believed that Pikmin resembled them. These look just like normal carrots; orange, small-sized, and having long leafy parts. These are seen in the in-game Piklopedia in Pikmin 2, and can be thrown at the Piklopedia's enemies/plants to see what reaction would occur, such as the creature moving or waking up, or eating and attacking the carrots.
Golden carrots
Golden pikpik carrots are completely golden, even the leafy stem. They are a bit longer than the orange variety, and have three curled roots, instead of the basic cone-shaped root. These are thought to be very valuable, and, at the beginning of Pikmin 2, Louie was instructed to perform a delivery with a cargo of such carrots. However, Louie had encountered a "ravenous space bunny" which ate the whole shipment. The truth might be different however...
After completing challenge mode with all pink flowers, you can see it was Louie who ate the golden Pikpik Carrots that he claimed were eaten by a space bunny.