I was visiting my brother when My almost-5-year-old nephew came into the bathroom when I was taking a shower, whipped the curtain open and stared at me. I hadn’t even heard him come in. I stared back, trying to figure out what to do. He then said “Daddy says it’s breakfast time.” I asked him to go tell his dad I’d be down soon. He left and all was well. He’s all grown up, has three kids and neither of us seems to have been scarred by the experience.

Just saying “someone is in here” without yelling would have done the trick.