I have to say silence or giggling. My wife had put our twin sons down for a nap one day. After a couple of hours, she was in the kitchen getting supper ready when she heard the twins giggling. She got suspicious and went into their bedroom. The next thing that I heard was the dreaded 'Honey, come in here!'. When I walked into the bedroom, the twins were standing at the rails of their cribs, smiling away! They were so proud of what they had done!
The reason they were so proud is they had shown a flash of their future artistic talent. Everywhere that they could reach was fingerprinted with shit from their diapers, including themselves! My wife was horrified, but I just roared with laughter...until I helped her clean everything up.
True story.