化身全真 Disguised as a Wandering Daoist
那大仙按落雲頭，搖身一變，變作個行腳全真。你道他怎生打扮：那大仙按落云头，摇身一变，变作个行脚全真。你道他怎生打扮：
逐句解 Line by line
The Great Immortal brought down his cloud, gave his body a shake, and changed into a wandering Quanzhen Daoist.
He does not arrive as himself. 搖身一變, yáo shēn yí biàn, "one shake of the body and he changed," is the novel's standard formula for a transformation — the same words used of Wukong a dozen times a chapter, here turned on him. 行腳全真, xíng jiǎo quán zhēn, is a wandering adept of the Quanzhen school, one of the two great orders of later Daoism, whose members took vows and travelled; 行 is xíng, "to walk, to travel." 按落雲頭, bringing the cloud down.
You ask how he was got up:
你道他怎生打扮, "and how do you suppose he was got up?" — the storyteller turning to the audience before a set-piece description. What follows is verse, and the switch is deliberate: the eye stops on the costume.
He wore a robe of a hundred patches, and girt on a Lü-Gong sash;
The costume is the disguise, and every item is correct for the type. 百衲袍, bǎi nà páo, a "hundred-patch robe," is the beggar-ascetic's coat pieced from rags — poverty worn as a badge. 呂公絛, lǚ gōng tāo, is a sash in the style of Lü Dongbin, the most famous of the Eight Immortals; 絛, tāo, is a woven cord, and 繫 here is jì, "to tie on." Wearing a Lü Dongbin belt is roughly like turning up in a particular saint's habit: it announces exactly which tradition you belong to.
in his hand he shook a deer-tail whisk, and softly beat a fisher-drum.
麈尾, zhǔ wěi, is a whisk made from the tail of the 麈, zhǔ, the elaphure or Père David's deer. It began as a fly-swat and became the emblem of the philosophical talker — something like a conductor's baton for metaphysics, waved to mark the turns of an argument. Remember it: it is the only weapon this man will use. 漁鼓, yú gǔ, the "fisher-drum," is a length of bamboo with a skin over one end, the busking instrument of wandering Daoists.
Three-eared straw sandals were on his feet, a nine-yang kerchief wrapped his head;
三耳草鞋, sān ěr cǎo xié, are straw sandals with three loops or "ears" for the laces. 九陽巾, jiǔ yáng jīn, the "nine-yang kerchief," is a Daoist headcloth; nine is the number of pure yang, so the name claims a great deal for a piece of cloth. 巾子 takes the toneless suffix 子, zi.
wind filled his fluttering sleeves, and from his lips rang the tune "The Moon on High."
And he arrives singing. 月兒高, Yuè'r Gāo, "The Moon on High," is a real tune-title, with the diminutive suffix 兒, ér. 飄飄風滿袖, piāo piāo fēng mǎn xiù, wind filling the fluttering sleeves — a line worth holding on to, since it is a sleeve that ends the fight.
Zhenyuan comes down as a 行腳全真, a wandering Quanzhen adept, and the verse kits him out in the complete uniform of the type: the hundred-patch robe, the Lü Dongbin sash, the deer-tail whisk and the fisher-drum, straw sandals and a nine-yang kerchief, with a popular tune on his lips. It is a portrait of the ideal Daoist beggar, assembled by a Patriarch of the Earthly Immortals playing dress-up.
The disguise is chosen with some wit. Of all the shapes available to him he picks the poorest and most harmless one in the Daoist repertoire — a man with no possessions, singing for his supper — and walks up to four fugitives with it. The elegance of the description is part of the trap: nothing here looks like a threat.
It is also the chapter turning its own devices around. Transformation and disguise have been Wukong's specialities for twenty-five chapters; here the same formula, 搖身一變, is used against him by someone better at it. Note the sleeve in the last line, filling with wind. That sleeve is going to swallow the whole party.