得勝貓兒 The Cat That Won
這大聖果然歡喜。古人云「得勝的貓兒歡似虎」也，只倚著強能，更不察來人的意思。見是個八戒的模樣，便就叫道：「兄弟，你往那裡去？」牛魔王綽著經兒道：「師父見你許久不回，恐牛魔王手段大，你鬥他不過，難得他的寶貝，教我來迎你的。」这大圣果然欢喜。古人云「得胜的猫儿欢似虎」也，只倚着强能，更不察来人的意思。见是个八戒的模样，便就叫道：「兄弟，你往那里去？」牛魔王绰着经儿道：「师父见你许久不回，恐牛魔王手段大，你斗他不过，难得他的宝贝，教我来迎你的。」
逐句解 Line by line
The Great Sage was indeed delighted.
果然 — sure enough. The storyteller confirms the Bull's forecast in his own voice one clause after it was made, without waiting to show the prediction coming true.
As the ancients said, "the cat that has won is as glad as a tiger"; and he, leaning only upon his own strength, did not look further into the intent of the one who came.
Here is the joke, and it is at the Great Sage's expense. 似 holds at sì in the comparing sense everywhere in this edition, and Chapter 59 reads it so at all six of its sites. 貓兒 takes the full ér rather than the light curled er: this edition splits 兒 by whether the thing is alive, giving ér to 蟲兒 and 孩兒 and er to 路兒, 袋兒, 車兒. 意思 keeps the full literary sī, not the modern light si; Chapter 59 has two occurrences and both are sī.
Seeing that it was Eight Rules' shape, he called at once: "Brother, where are you going?"
那裡 is the question word here — nǎ, "where" — not the pointing nà the same character carries six times elsewhere in these few passages. Nothing in the writing marks the difference; you have to take it from the sense every single time.
The Bull Demon King, catching up the thread, said: "Our master, seeing you so long in returning, feared the Bull Demon King's powers were great, that you would be no match for him in a fight and would find it hard to obtain his treasure, and so sent me to come and meet you."
The false Eight Rules speaks with unnerving fluency. 綽 is chāo, the vernacular spelling of 抄, to snatch up — 綽著經兒 is to grab the thread and run with it. The nickname reading chuò belongs only to 綽號, and 康熙 licenses it under 昌約切 alone. 經兒 takes the light er. 難得 reads dé, since 得 governs 他的寶貝 directly.
The proverb is the heart of the passage and the storyteller picked it carefully. 得勝的貓兒歡似虎 — a cat that has caught something is as pleased as a tiger. Which is to say it swaggers about like a far more dangerous animal, on the strength of one success. The Great Sage has beaten the Bull twice, robbed his wife and stolen his mount, and the storyteller's verdict on all of it is: cat.
更不察來人的意思 states the failure precisely. It is not that the disguise was flawless. It is that no examination took place at all. The Bull is standing there inside his enemy's own borrowed trick, one day old, and the enemy does not look.
Listen to how the fake Eight Rules talks. He names the Bull Demon King in the third person, credits him with great powers, and predicts the Great Sage's defeat — all of it flattering to say aloud, all of it calculated to produce exactly the correction it duly produces. 綽著經兒, catching up the thread, is the storyteller's word for the technique: the Bull invents no story, he simply takes hold of the one his listener is already telling himself.