I was in high school and lived with my parents at the time. We lived in a nice town in a quiet neighborhood, so we didn't lock our doors. It was summertime and I didn't have any responsibilities, so I stayed up really late most nights. I hung out in the basement so I could watch TV and play video games without worrying about being too noisy. At the time, my grandfather (my dad's dad) had cancer, and only had another month or two to live. It affected my dad a lot. On occasion, he would wake up in the middle of the night, unable to sleep. He'd pour himself a drink and sit on the deck to think.
One night I was playing a game and got kind of hungry, so I headed upstairs to the kitchen to grab a drink and a snack. Our basement was really dark, so when I came upstairs I didn't have to turn any lights on; my eyes were already adjusted. As I walked into the kitchen, I noticed someone on our back deck walking towards the back slider. I paid it no mind, thinking it was my dad returning to bed.
"You doing alright, Dad?" I asked as he stepped inside. After no response for a few seconds I looked at him and asked again "Dad?"
Finally a voice I don't recognize says in an embarrassed and terrified tone "You... uh... caught me! Good work!" He immediately turned around and ran out the door. Confused, I ran up to the door after him and started yelling. "Who the hell are you? Get off our property!" but he disappeared into the woods. We started locking our doors after that.
TL;DR: Scared off a burglar by thinking he was my dad.