I heard that

Today as we were leaving to take Will to school, Olivia threw her shoes down the stairs (rather than taking them like I had asked her to).
"Olivia - we don't throw our shoes down the stairs. Go get them and put them on so we can take Will to school"
Will (whispering): Throw my shoes down.
"Will, don't tell your sister to do something I just told her not to do!"
"Mom! How did you hear that? I said it in super quiet voice!"
"Because Will, I can hear everything you say - and I know everything you do too - so don't try and pull anything over on me."

Let's just hope that will leave a lasting impression.