She looked as if she had been poured into her clothes and had forgotten to say "when."

Wodehouse’s line is a comic simile aimed at a figure whose clothing is so tight and form-fitting that it seems liquid had been “poured” onto the body. The added twist—“and had forgotten to say ‘when’”—extends the metaphor into a joke about excess: the pouring never stopped, so the clothes cling almost implausibly. Beyond the immediate visual gag, it also reflects Wodehouse’s characteristic light satire of fashion and social display, where appearance is exaggerated into absurdity. The humor depends on timing and understatement: the sentence sounds politely descriptive while delivering a sharp, playful jab.