What is one thing you caught your child doing that you wish you had never seen?

My friend told me she saw her son play with his own poop once. He is potty trained and when he was doing his business, she took her eyes off him for 10 seconds to wash her sink only to catch him nearly putting a piece of poop into his mouth. She was glad she stopped him in the nick of time but at the same time, she wished it didn't happen. The memory is etched in her mind forever, she says haha.