When my DD was a toddler and almost ready for a toddler bed, she had a habit of crawling out of her crib and prowling the house way to early in the morning. So I started putting up the side of her crib again. One very early morning we were all in bed and I could hear her talking to herself in her crib. All of a sudden the doorbell rang and it was the paperboy.
After my DH paid the paperboy he got back into bed. All of a sudden from her room we heard "Ding Dong". guess that was our wake-up call. Pretty clever for a tot!