A Guider I know took her Brownies away for a week & reminded them each morning they were to put on a clean pair of knickers.
On the last day, when they were packing, one wee lass had no dirty undies to pack. Turned out that, as no one had said to take the dirty knickers off she'd just been layering up. It was back when Brownies wore dresses, but you'd still think someone might've noticed there was something awry...