Tripitaka or Xuanzang
The monk Xuanzang (also referred to in the story as Tang Sanzang, meaning "Tang Tripitaka Master", with Tang referring to the Tang Dynasty and Sanzang referring to the Tripitaka, the main categories of texts in the Buddhist canon which is also used as an honorific for some Buddhist monks) is a Buddhist monk who had renounced his family to become a monk from childhood. He is just called Tripitaka in many English versions of the story. He set off for Dahila kingdom (天竺国, an appellation for India in ancient China) to retrieve original Buddhist scriptures for China. Although he is helpless in defending himself, the bodhisattva Avalokiteśvara (Guanyin) helps by finding him powerful disciples who aid and protect him on his journey. In return, the disciples will receive enlightenment and forgiveness for their sins once the journey is done. Along the way, they help the local inhabitants by defeating various monsters and demons who try to obtain immortality by eating Xuanzang's flesh.
Monkey King or Sun Wukong
Sun Wukong is the name given to this character by his teacher, Subhuti, the latter part of which means "Awakened to Emptiness" (in the Waley translation, Aware-of-Vacuity); he is called Monkey King. He is born on Flower Fruit Mountain from a stone egg that forms from an ancient rock created by the coupling of Heaven and Earth. He first distinguishes himself by bravely entering the Water Curtain Cave on the mountain; for this feat, his monkey tribe gives him the title of "Handsome Monkey King". After angering several gods and coming to the attention of the Jade Emperor, he is given a minor position in heaven as the Keeper of Horses (弼马温) so they can keep an eye on him. This job is a very low position, and when he realises that he was given a low position and not considered a full-fledged god, he becomes very angry. Upon returning to his mountain, he puts up a flag and declares himself the "Great Sage Equal to Heaven." Then the Jade Emperor dispatches celestial soldiers to arrest Sun Wukong, but no one succeeds. The Jade Emperor has no choice but to appoint him to be the guardian of the heavenly peach garden. The peaches in the garden bear fruit every 3,000 years, and eating its flesh will bestow immortality, so Sun Wukong eats one and becomes more powerful and near-matchless. Later, after fairies who come to collect peaches for the heavenly peach banquet inform Sun Wukong he is not invited and make fun of him, he starts causing trouble in Heaven and defeats an army of 100,000 celestial troops, led by the Four Heavenly Kings, Erlang Shen, and Nezha. Eventually, the Jade Emperor appeals to the Buddha, who detains Wukong under a mountain called Five Elements Mountain. Sun Wukong is kept under the mountain for 500 years, and cannot escape because of a spell that was put on the mountain. He is later set free when Xuanzang comes upon him during his pilgrimage and accepts him as a disciple.
His primary weapon is his staff, the "Ruyi Jingu Bang", which he can shrink down to the size of a needle and keep in his ear, as well as expand it to gigantic proportions. The rod, which weighs 17,550 pounds, was originally a pillar supporting the undersea palace of the Dragon King of the East Sea, but he was able to pull it out of its support and can swing it with ease. The Dragon King had told Sun Wukong he could have the staff if he could lift it, but was angry when the monkey was actually able to pull it out and accused him of being a thief; hence Sun Wukong was insulted, so he demanded a suit of armour and refused to leave until he received one. The Dragon King, unwilling to see a monkey making troubles in his favourite place, also gave him a suit of golden armour. These gifts, combined with his devouring of the peaches of immortality, three jars of elixir, and his time being tempered in Laozi's Eight-Trigram Furnace (he gained a steel-hard body and fiery golden eyes that could see very far into the distance and through any disguise. He is therefore always able to recognise a demon in disguise while the rest of the pilgrimage cannot. However, his eyes become weak to smoke), makes Sun Wukong the strongest member of the pilgrimage by far. Besides these abilities, he can also pluck hairs from his body and blow on them to convert them into whatever he wishes (usually clones of himself to gain a numerical advantage in battle). Although he is a master of the 72 methods of transformation (七十二变), and can transform into a bird (giving him the ability to fly), he can use his "somersault cloud" enabling him to travel vast distances in a single leap. The monkey, nimble and quick-witted, uses these skills to defeat all but the most powerful of demons on the journey.
Sun's behavior is checked by a band placed around his head by Guanyin, which cannot be removed by Sun Wukong himself until the journey's end. Xuanzang can tighten this band by chanting the "Ring Tightening Mantra" (taught to him by Guanyin) whenever he needs to chastise him. The spell is referred to by Xuanzang's disciples as the "Headache Sutra", which is the Buddhist mantra "oṃ maṇipadme hūṃ". Xuanzang speaks this mantra quickly in repetition.
Sun Wukong's childlike playfulness is a huge contrast to his cunning mind. This, coupled with his great power, makes him a trickster hero. His antics present a lighter side in what proposes to be a long and dangerous trip into the unknown.
Zhu Bajie (literally "Pig of the Eight Prohibitions") is also known as Zhu Wuneng ("Pig Awakened to Ability"), and given the name Pigsy, Monk Pig or just simply Pig in English.
Once an immortal who was the Marshal of the Heavenly Canopy commanding 100,000 naval soldiers of the Milky Way, he drank too much during a celebration of gods and attempted to flirt with the moon goddess Chang'e, resulting in his banishment into the mortal world. He was supposed to be reborn as a human, but ends up in the womb of a sow due to an error at the Reincarnation Wheel, which turns him into a half-man half-pig monster. Zhu Bajie was very greedy, and could not survive without eating ravenously. Staying within the Yunzhan Dong ("cloud-pathway cave"), he was commissioned by Guanyin to accompany Xuanzang to India and given the new name Zhu Wuneng.
However, Zhu Bajie's indulgence in women led him to the Gao Family Village, where he posed as a normal being and wedded a maiden. Later, when the villagers discovered that he was a monster, Zhu Bajie hid the girl away, and the girl wailed bitterly every night. At this point, Xuanzang and Sun Wukong arrived at the Gao Family Village and helped defeat him. Renamed Zhu Bajie by Xuanzang, he consequently joined the pilgrimage to the West.
His weapon of choice is the jiuchidingpa ("nine-tooth iron rake"). He is also capable of 36 transformations (as compared to Sun Wukong's 72), and can travel on clouds, but not as fast as Sun. However, Zhu is noted for his fighting skills in water, which he used to combat Sha Wujing, who later joined them on the journey. He is the second strongest member of the team.
Shā Wùjìng (literally meaning "Sand Awakened to Purity"), given the name Friar Sand or Sandy in English, was once a celestial Curtain Lifting General, who stood in attendance by the imperial chariot in the Hall of Miraculous Mist. He was exiled to the mortal world and made to look like a monster because he accidentally smashed a crystal goblet belonging to the Queen Mother of the West during a Peach Banquet. The now-hideous immortal took up residence in the Flowing Sands River, terrorising surrounding villages and travellers trying to cross the river. However, he was subdued by Sun Wukong and Zhu Bajie when Xuanzang's party came across him. They consequently took him in, as part of the pilgrimage to the West.
Sha's weapon is the yueyachan ("Crescent-Moon-Shovel" or "Monk's Spade"). He also knows eighteen transformation methods and is highly effective in water combat. He is about as strong as Zhu Bajie, and is much stronger than Sun Wukong in water. However, Zhu can defeat Sha in a test of endurance, and Sun can almost certainly defeat him both on land and in the air.
Sha is known to be the most obedient, logical, and polite of the three disciples, and always takes care of his master, seldom engaging in the bickering of his fellow disciples. He has no major faults nor any extraordinary characteristics. Perhaps this is why he is sometimes seen as a minor character. He does however serve as the peacekeeper of the group mediating between Sun and Zhu and even Xuanzang and the others. He is also the person whom Xuanzang consults when faced with difficult decisions.
Sha eventually becomes an arhat at the end of the journey, giving him a higher level of exaltation than Zhu Bajie, who is relegated to cleaning every altar at every Buddhist temple for eternity, but lower spiritually than Sun Wukong or Xuanzang, who are granted Buddhahood.