運去遇佳人 Fortune Out Fair Lady In
行者只是冷笑不止。唐僧罵道：「潑猴頭，你笑怎的？」行者道：「我笑你時來逢好友，運去遇佳人。」行者只是冷笑不止。唐僧骂道：「泼猴头，你笑怎的？」行者道：「我笑你时来逢好友，运去遇佳人。」
逐句解 Line by line
Pilgrim only went on smiling coldly and would not stop.
冷笑 is the cold smile of somebody who has been overruled and is waiting. It is the whole of his contribution to the rescue.
The Tang Monk scolded him: "Wretched monkey head, what are you laughing at?"
罵 is stronger than scolding — it is abuse. Tripitaka uses it twice in three lines, which for a monk is a notable quantity of temper.
Pilgrim said, "I am laughing that when your luck comes in you meet good friends, and when your luck runs out you meet a beautiful woman."
He has bent a proverb. The usual pairing runs on good fortune bringing good company; Pilgrim keeps the first half and replaces the second with a beauty, so that the balanced shape of the saying does the insult for him. It sounds like received wisdom and is nothing of the kind.
This is Pilgrim at his most economical. He cannot argue the point again, so he smiles until he is asked why, and then delivers a line that is not quite a proverb and cannot quite be answered.
The joke works because Chinese proverbs come in matched halves, and a matched half carries authority regardless of what is in it. He has smuggled a private opinion into the shape of common wisdom, which is exactly what the demon did to his master an hour ago with the pagoda.