Pikpik carrot
Pikpik carrots are vegetables native to Captain Olimar's home planet, Hocotate. In the Pikmin, it is stated that Olimar's favorite soup contains "three large onions and hundreds of miniature red, yellow, and blue carrots". The reason Pikmin have their name is because Olimar believed that Pikmin resembled them, and they live in crafts that resemble onions, which also reminds him of his favorite soup. In Pikmin 2, pikpik are seen in the in-game Piklopedia and look just like normal carrots; orange, about the size of a Pikmin, and having long leafy parts. These 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...