Twoleg

Twoleg is the Clan term for humans.

General
Twolegs are tall, smooth-skinned creatures with removable pelts to keep them warm, and some fur on their heads and occasionally on their faces. They stay in areas called Twolegplaces, look after kittypets, dogs, and other animals. They occasionally ride in the bellies of monsters, or on the backs of horses. They live in large, boxy nests with hard roofs and floors surrounded by neat gardens and fences. They also seem to like dogs.

Twolegs are also known by cats as housefolk, workfolk, Upwalkers, or Nofurs. The Clan cats find their gestures, motives, and habits strange, and they do not understand why Twolegs do such things.

Language
Twoleg language seems to come across to Clan cats as angry gibberish, although kittypets seem to understand Twoleg speech to some extent. For example, Rusty, Princess, and Sasha are aware of their names given them by their owners, and also of the names of their owners. Purdy says, "Upwalkers called me different names... the Upwalker who had the fire called me Purdy." Additionally, kittypets apparently know the Twoleg words for certain Twoleg-related things and concepts, for instance the names of rooms in a house.

Structures and Monsters
Throughout the series, Twolegs have brought all sorts of strange things into the world of the Clans. Cats regularly see Twolegs sitting in various types of monsters (vehicles such as cars and trucks), and even ones that float on water, which they refer to as water-monsters (motor boats). The Clan cats are rightfully scared of the monsters for reasons other than the noise. Twoleg monsters have tried hitting cats in the past. They occasionally succeed as with Cinderpaw and Whitethroat. Cinderpaw was maimed for life after a monster ran over her leg, whilst Whitethroat was crushed instantly.

They also see Twoleg houses, which are known to them as dens or nests, and feel uncomfortable inside them because of the enclosed space inside the roof and walls. A few notable Twoleg structures are Barley's Farm, the abandoned nest in the ThunderClan lake territory, the Horseplace, Firestar's previous home, Princess' home, Susan and Jacques' home, the Greenleaf Twolegplace, and the Halfbridges.

Relation to Clan cats
Most Twolegs like cats, but they typically cause trouble for them because of their ignorance, such as:
 * They disturb Clan cats and scare away prey when coming to the forest in greenleaf to camp and swim.
 * They often try to capture Clan cats and rogues to keep them as kittypets. Mostly RiverClan suffers of this, as their territory has the most Twoleg activity and their warriors are plump enough to be mistaken for kittypets - many of their warriors have been captured and taken away.
 * In Forest of Secrets, they scare away many of the fish that feed RiverClan by invading the shores of the river and polluting it, forcing the normally prosperous Clan into near starvation.
 * Throughout the course of Moonrise and through Dawn, Twolegs impact the Clans' livelihoods in several ways, including poisoning the rabbits on WindClan territory, capturing Clan cats and rogues, and destroying the forest itself, which forces the Clans to flee the forest for a new territory.
 * In Twilight, RiverClan kits find and taste a liquid Twoleg substance (supposedly battery acid) in their territory, and many cats fall ill (or even die) because of the poisoning.
 * In Sunset, they set fox traps in ThunderClan territory; Berrykit gets trapped in one, losing his tail and Firestar nearly loses all his remaining lives at once after being driven into one by Hawkfrost.
 * Some Twolegs dislike stray cats and will try to harm them (usually to protect their kittypets), for example Susan's and Jacques' housefolk, or Petal's housefolk.
 * They also took Cloudpaw because he came from door to door knocking and asking Twolegs for food. Cloudpaw lied when he returned to ThunderClan, saying that he was "forced into their nest and their food tasted like crowfood."
 * Twolegs are seen observing beavers damming a stream in the The Fourth Apprentice.

Housefolk
"Housefolk" is the kittypet term for Twolegs, usually referring to their owners. They are much kinder than workfolk, as stated several times by Cody.

In Dawn, Leafpaw is speaking to Firestar about Cody leaving. Firestar says that she probably misses her housefolk, and Leafpaw is surprised to hear her father use a kittypet word.

Workfolk
Workfolk are mostly construction workers but just about any worker falls in this category. They are seen in The New Prophecy series, when they come to tear down the forest. They ride in tree-eaters instead of monsters, and often stray off the Thunderpath.

Twoleg Kits
Twoleg Kit is the Clan word for human babies, toddlers, and younger children. They are always seen with full grown Twolegs.

Veterinarian
Cody describes veterinarians as "Twoleg medicine cats" who heal kittypets and other animals, and have much more medicines to work with than Clan cats do.

A specific type of veterinarian is the Cutter, one that spays or neuters cats.

Ken and Jean
Ken and Jean were elderly Twolegs, the owners of Sasha. Jean dies from sickness, and Ken moves for a retirement home (and later dies as well). As a result, Sasha leaves the nest and becomes a rogue.

Petal's Housefolk
The owner of the kittypet Petal (who later becomes Petalnose in Firestar's Quest) is an elderly man who lives in a run-down house in the wilderness. He locks Petal in his house, and does not give her enough food, although Petal has to feed her kits. He doesn't like Rainfur especially, and is often seen throwing objects at cats. Firestar and Rainfur rescued Petal despite the Twoleg's efforts to stop them. Also, in SkyClan's Destiny, it is learned that they keep a SkyClan warrior named Shrewtooth prisoner.

Trivia

 * Twoleg is always spelled with a capital T, as if it is a Clan name.
 * Despite posing a constant threat towards the Clans, no Twoleg is ever killed in the series. This is most likely to avoid controversy and accusations of being immoral.