Grunties are pig-like creatures that players of The World can raise in Root Towns as virtual pets. As a type of NPC, most Grunties can speak. Their backstory, appearance, and uses are dramatically different between the two different versions of The World.
In The World, Grunties are used as a method of transportation across fields, useful for avoiding Magic Portals. According to the mythology of The World, Grunties are the messengers of the great god Hebiguso, and the inhabitants of The World care for them to gain his favor. Players start out with a Baby Grunty, and by finding and feeding them various kinds of Grunty Food, the player can raise the baby into various kinds of Grunties, each with their own distinct personality and abilities, and an inventory of items to trade.
The types available vary from server to server. After all the types of Grunties available on a server have been raised, Grunty Racing becomes available. While Grunties weren't allowed to leave their home server during the .hack games, it seems this restriction was lifted later on, as Hotaru and Komiyan III were both able to bring their Grunties with them when they changed servers during .hack//Legend of the Twilight.
Grunties who are neglected by their owners will eventually come down with the Grunty Flu. Numerous items can cure this flu but it depends on what stage the flu is at. The more advanced the flu, the more rare and difficult the item is to obtain.
In The World R:2, Grunties are kept as pets, and act as guild mascots and "greeters" to people visiting foreign guilds. Grunties retain the same basic appearance as in the previous rendition of The World, but they are shorter, thinner, and stand on two legs. They manage guild @HOMEs and take on the appearance and personality of the guildmaster. An exception is Mecha Grunty, who is found deserted in areas and can be saved by players willing to power it up with Chim Spheres. The three treasures of the Grunty race are event items in The World R:2, used in Haseo's quest to become a guildmaster. They consist of the Grunty Hat (obtained from Gao Grunty), the Grunty Shoes (obtained from Melo Grunty), and the Grunty Brush (obtained from Wise Grunty). They are a parody of the Imperial Regalia of Japan. The following are the Grunties seen in The World R:2.