How oh how do they know?

Why is it when you finally get one kid to sleep and you sneak off to take a shower in peace that the other one, the one who was napping soundly--snoring even--instinctively gets up, and then when that one is finally napping again, the first one decides to get up two minutes after?

And then the next thing you know it's 3:47 in the afternoon when the hubby finally gets back from the Doctor's and he looks at you like you are some sort of slob because you are still in pajamas, and now that you FINALLY have the opportunity to bathe, it seems like such a waste of time, but you do it anyways just for the 15-minute break and to feel like a human for a few hours afterwards.