剝皮亭 The Pavilion Of Flayed Skins
正欲看看洞景，只聞得猩猩出語道：「有來有去，你回來了？」行者只得答應道：「來了。」猩猩道：「快走，大王爺爺正在剝皮亭上等你回話哩。」正欲看看洞景，只闻得猩猩出语道：「有来有去，你回来了？」行者只得答应道：「来了。」猩猩道：「快走，大王爷爷正在剥皮亭上等你回话哩。」
逐句解 Line by line
He was about to take a look at the cave when he heard a gorilla speak up: "There-and-Back! Are you back?"
聞得 takes dé. The gorilla is the animal the muster poem singled out for understanding human speech, and it is the one that stops him — so the description turns out to have been a warning, and he had read it as scenery.
Pilgrim had no choice but to answer: "I am back."
應 is yìng, to answer back, not the yīng of ought to. 只得 is could do nothing but: the disguise has started working faster than he wanted, and his first line inside it is two characters he did not choose.
The gorilla said: "Get along. His Lordship the Great King is up in the Flaying Pavilion waiting to hear your report."
剝皮亭 is the pavilion where skins are taken off, and it is named here for the first time, in passing, as an address. 爺爺 keeps a full first syllable and a light second.
The disguise is challenged before it has been tested, and it holds — because the challenge is friendly. The gorilla is not checking anything; it is greeting a colleague and then chasing him along. Wukong answers in two characters and gives away nothing, which is the only sensible move when you have no idea what the dead man sounded like.
The name is doing the work. He said it aloud on an empty road as a joke about a corpse; the gorilla now uses it as a form of address, and the joke has become a passport. Nothing else about him is examined.
And the destination gets its name at the very end of the passage, as an ordinary piece of geography. The Great King is waiting in the pavilion where skins are taken off. Nobody remarks on it, and Wukong is being sent there wearing one.