明知故問 Feigned Ignorance
行者明知故問道：「你二位從那裡來的？」那怪道：「自蓮花洞來的。」「要往那裡去？」那怪道：「奉我大王教命，拿孫行者去的。」行者道：「拿那個？」那怪又道：「拿孫行者。」孫行者道：「可是跟唐僧取經的那個孫行者麼？」那妖道：「正是，正是。你也認得他？」行者道：「那猴子有些無禮。我認得他，我也有些惱他。我與你同拿他去，就當與你助功。」行者明知故问道：「你二位从那里来的？」那怪道：「自莲花洞来的。」「要往那里去？」那怪道：「奉我大王教命，拿孙行者去的。」行者道：「拿那个？」那怪又道：「拿孙行者。」孙行者道：「可是跟唐僧取经的那个孙行者么？」那妖道：「正是，正是。你也认得他？」行者道：「那猴子有些无礼。我认得他，我也有些恼他。我与你同拿他去，就当与你助功。」
逐句解 Line by line
Pilgrim, knowing full well, asked as if he didn't: "Where do you two come from?"
明知故問 (míng zhī gù wèn), "to know perfectly well and ask anyway," is still one of the most-used phrases in Chinese -- what you say to someone being disingenuous on purpose. Here the storyteller uses it as a stage direction. 那裡 is the question-word nǎ, "where."
The imps said: "We come from the Lotus-Flower Cave." "And where are you bound?"
蓮花洞, the Lotus-Flower Cave. 要往那裡去 (yào wǎng nǎ lǐ qù), "and where are you headed" -- 那 again nǎ. He asks it the way a man asks about the weather.
The imps said: "On our king's orders, we're off to catch Sun Pilgrim."
奉...教命 (fèng... jiào mìng), "in obedience to the command of." And out it comes: they announce their errand, which is to catch Sun Pilgrim, to Sun Pilgrim.
Pilgrim said: "Catch whom?" The imps said again: "Catch Sun Pilgrim."
拿那個 (ná nǎ gè), "catch which one?" -- the question-word nǎ again, deadpan. He makes them say it twice.
Sun Pilgrim said: "You mean that Sun Pilgrim who's fetching scriptures with Tripitaka?"
取經 (qǔ jīng), "to fetch the scriptures," the phrase that names the entire journey. And here 那個 flips to the pointing nà, "that Sun Pilgrim" -- one character, two readings, in adjacent lines, and the flip is the joke's timing: he stops asking which one and starts pointing at himself.
The imps said: "The very one, the very one. Do you know him too?"
認得 (rèn de), "to know, to be acquainted with," toneless 得. The imps are delighted. They think they have found a witness.
Pilgrim said: "That monkey's a rude sort. I know him, and I've a bit of a grudge against him myself.
無禮 (wú lǐ), "no manners." 惱 (nǎo), "to be annoyed with." Pilgrim slanders himself in mild, plausible terms -- not a monster, just a bit rude -- which is far more convincing than praise would have been.
"I'll go catch him with you — count it as my lending a hand."
就當 (jiù dàng), "just count it as," 當 read dàng, "to reckon as." 助功 (zhù gōng), "to lend a hand toward the job." He has now talked his way onto the team hunting him.
The comedy sharpens to its finest point. Pilgrim knows perfectly well and asks anyway, and the imps announce their errand -- to catch Sun Pilgrim -- to Sun Pilgrim's face. His deadpan follow-ups have the timing of a practiced comedian: catch whom? that Sun Pilgrim, the one fetching scriptures? He draws it out while they, all innocence, confirm every detail.
Then he closes the con by slandering himself. That monkey is a rude sort, and I have a grudge against him too. The self-abuse is a small masterpiece of misdirection, because a stranger with his own complaint against Monkey is exactly the ally two imps on this errand would want. Everything is now in place for him to get his hands on the treasures, and the grammar joins in: 那 turns from the questioning nǎ to the pointing nà at the precise moment he starts pointing at himself.