I’ve written several articles on the worship of the Monkey King. I’ve decided to post a succinct overview for those not familiar with the subject.
Warning: Self-mortification and blood below!
Sun Wukong is worshiped in southern China, Taiwan, and areas of Southeast Asia, including Malaysia, Singapore, and even Thailand, as the “Great Sage Equaling Heaven” (Qitian dasheng, 齊天大聖) (fig. 1). Variations of this title often include “Lord” (ye, 爺) or “Buddha” (fozu, 佛祖). He is very rarely addressed as the “Victorious Fighting Buddha” (Dou zhansheng fo, 鬥戰勝佛), which is taken from the end of Journey to the West (1592) when our hero is bestowed Buddhahood for protecting the monk Tripitaka. This is the name of a real world deity that was only later associated with Monkey in literature. I’ve even seen one temple that mixed such titles to call him the “Fighting Sage Buddha” (Dou zhan sheng fo, 鬥戰聖佛).
An awesome gourd-bearing Great Sage statue from Taiwan (larger version). It is one of a trinity. Photo by the author.
The Great Sage’s worship can be traced to Fujian province, China, from where it spread out to other countries, including 19th-century America. Published references to his worship in Fujian go back to at least the 17th-century, though one 13th-century stone pagoda depicts Monkey as a sword-wielding protector deity, among other heavenly guardians, bodhisattvas, patriarchs, and eminent monks, suggesting that he may have been revered in earlier times. His worship was so well-known in Fujian during the early Qing-period that it was criticized in the famed Strange Tales from a Chinese Studio (Liaozhai zhiyi, 聊齋誌異, 1740), a collection of popular stories.
My friend has visited several Great Sage temples in Fujian. I’ve visited 14 temples in Taiwan (so far). I even discovered a holy scripture associated with the monkey god titled “The Great Sage Equaling Heaven’s True Scripture of Awakening People and Enlightening the World” (Qitian Dasheng xingren jueshi zhenjing, 齊天大聖醒人覺世眞/真經). A brief analysis of the scripture by my friend can be seen here.
Much like Sun Wukong can multiple his body, his religion recognizes multiple Great Sages, each with their own holy and/or administrative function. Although, temples apparently believe each Great Sage is an emanation of the singular deity. This multiplicity of usually 3 to 5 figures (with dozens of soldier monkeys) may be traced to different sources. For instance, an early 15th-century play predating the novel describes Monkey as one of three brothers and two sisters. It surprisingly refers to Wukong, the middle brother, as the “Great Sage Reaching Heaven” (Tongtian dasheng, 通天大聖), while the older brother is called the Great Sage Equaling Heaven. The youngest, the “Third Son Shuashua” (Shuashua sanlang, 耍耍三郎/爽爽三郎), appears as a white-faced figure among a color-coded trinity in one Fujian tradition (fig. 2). The Great Sage Reaching Heaven graces the trinity with a black face. Rounding out the group with a red face, the Cinnabar Cloud Great Sage (Danxia dasheng, 丹霞大聖), a separate figure not from the play, appears in a 17th to 18th-century pious novel which describes his evil deeds, punishment, and rehabilitation by a Fujian goddess. Therefore, the multiple Great Sages share a connection to theater and religious literature.
As mentioned, various soldier monkeys serve in the Great Sage’s spiritual army. He leads five heavenly generals, representing the Chinese cardinal directions, each with their own armies. The demon queller, the “Third Prince” (San taizi, 三太子; a.k.a. Nezha), serves as his vanguard. The Third Prince can often be seen positioned on a table in front of the main altar, or riding a palanquin and leading the way during religious processions. At least in Taiwan, the power of this spiritual army needs to be replenished during a yearly trip south to the island’s oldest monkey god house of worship, Wanfu Temple (Wanfu an, 萬福庵), which is considered a fount of pure energy. This is done by retrieving scoops of holy incense ashes from the main incense pot and bringing them back to the home temple pot. I saw one temple protect the ashes in a small, metal, building-shaped altar sealed with blood-consecrated paper talismans (fig. 3). It was then shaded with two processional flags and an eight trigrams umbrella (fig. 4). I was told exposing the ashes/soldiers to sunlight was considered highly disrespectful.
While considered a full-fledged god or even Buddha, the Great Sage is not a supreme deity. In fact, Buddho-Daoist folk religion considers him to be an intermediary for higher-ranking figures. For example, in some traditions he is a subordinate of the Bodhisattva Guanyin.  One temple in Taiwan even believes he answers to the martial god Guan Yu. Either way, he is considered the exorcist par excellence and a protector of children. The little ones whom he takes as his godchildren are known in Singapore as “dedicated children” (khoe-kia). Those under his protection are believed to grow up to become well-behaved adults.
Spirit-mediums (Taiwanese Hokkien: Tangki, 童乩; Chinese: Jitong, 乩童; literally: “Divining Child”) play a large part in the Great Sage’s religion. They are believed to channel his spirit to interact with believers, generally answering their questions, blessing them or their belongings with paper talismans, or prescribing medicine. On special occasions, they also perform a complex self-mortification ceremony; for instance, the mediums of one Taiwanese temple walk a pattern in between five ritual fires representing heavenly generals of the five directions, while flogging themselves with a sword, an ax, a spiked club, a sawfish nose sword, and a spiked ball, respectively. However, I’ve found that self-mortification tends to be more extreme in Southeast Asia, with mediums piercing their cheeks and bodies with lances, swords, hooks, and even bicycles! The ritual serves several purposes. First, hacking, skewering, and poking the body with various weapons is considered a form of self-sacrifice. Second, the weapons that pierce the flesh are believed to imbue the mediums with spiritual power needed in their battle with demonic forces that pervade every corner of daily life. Third, the resulting blood is believed to have demonifugic properties, hence the reason it is smeared on paper talismans and clothing. Overall, the ritual is performed to exorcize evil spirits that cause bad luck and mental and physical illnesses.
Fig. 5 – A spirit-medium channeling the Great Sage. He smiles in defiance after flogging his head with a spiked ball (larger version). Original photo by Cai Zhizhong (蔡志忠) (used with permission).
Mediums wear ritual bibs normally associated with babies in Asian culture. As noted above, the Hokkien/Chinese word for spirit-medium means “Divining Child”. This refers to the centuries-old belief that children were the mouthpieces of gods. In fact, the mediums are known to speak in a shrill voice known as “shen (神, god) language”. The fact that their back is bare refers to ancient Shang–Zhou period rituals in which a sacrificial victim was exposed to the elements. However, it should be noted that, since the 1980s, more and more mediums in Singapore have taken to wearing flashy, Chinese opera-inspired costumes, including the golden fillet.  I’ve seen one such medium that even wears a faux fur cowl and gloves during performances.
When not consulting a spirit-medium, the presence of the Great Sage can be determined by a glass vessel called the “Great Sage bottle” (Dasheng ping, 大聖瓶). It comprises a normal glass container (sometimes a soda bottle or something more elegant) filled with “noon water” (wushi shui, 午時水) and topped with a special bulbous glass stem. The bottle is believed to make a characteristic “ping-pong” (乒乓) chime upon the deity’s arrival in a temple or home, usually around 12 noon but also other times. I’ve heard of the vessel’s use in Taiwan, Hong Kong, and Singapore.
The Great Sage’s religious birthday is celebrated on different dates according to the location. It is the 16th day of the 8th lunar month in Hong Kong and Singapore, the 23rd (Fuzhou) or 25th day (Putian) of the 2nd lunar month in Fujian (sources vary), and the 12th day of the 10th lunar month in Taiwan. The celebration usually involves gifts of fruit, sweets, and liquor; self-mortification rituals by spirit-mediums; chanting performances by Daoist associations (see this video by me, for example); the burning of effigies and spirit money; group prayer; and sometimes lion/dragon dance performances by local martial arts clubs. Regarding this last note, martial artists have revered Wukong for centuries. He was even channeled by fighters of the Boxer Rebellion during the 19th-century.
Fig. 6 – Drawings of the japsang effigies of Korea. The first four figures are commonly associated with Tripitaka, Sun Wukong, Zhu Bajie, and Sha Wujing (larger version). However, contemporary sources sometimes named the first figure Wukong. This would make since as he’s wearing armor.
I should point out that Great Sage worship is not unique to people of Chinese descent. He was at some point absorbed into the religion of the Qiang ethnic group. The Qiang people revere a golden, stone-born monkey that is believed to have both stolen fire from the celestial realm and helped recover lost religious knowledge by creating a drum from the skin of a goat that had eaten their sacred scriptures. Wukong is sometimes equated with the monkey deity given the similarities in their respective lithic origins and penchant for stealing from heaven. The Great Sage is particularly worshiped by the red shamans as their patron deity, or “father god” (abba mula), for his skills in exorcizing evil. He is also sometimes equated with the ancestor from Qiang myth, who is believed to be a monkey-turned-man who married a heavenly goddess and fathered the human race.
Interestingly, Sun Wukong is even revered in Korea. While not officially worshiped as a deity (at least not by people of non-Chinese descent), he appears with a host of other mythological animals on the roof-hips of royal palaces to guard such important structures against fires and evil spirits (fig. 6). These clay effigies are known as japsang or chapsang (잡상; Ch: zaxiang, 雜像; “miscellaneous figurines”). 
1) I’ve had a few people ask me how a Buddha can be below a Bodhisattva. Normally, this isn’t the case, but Guanyin is just so incredibly popular in Asia. Her adoration in the east predates the Monkey King’s cult by many hundreds of years.
2) For more info on Asian spirit-mediums, see Chan (2006)
3) I’m currently writing an article on the japsang. I will post it in the coming weeks.
Chan, M. (2006). Ritual is Theatre, Theatre is Ritual: Tang-ki – Chinese Spirit Medium Worship. Singapore: Wee Kim Wee Centre, Singapore Management University.