I think I was in 4th or 5th grade. There was a boy, Dennis Evans, who I used to play with. One afternoon, Dennis, another boy and I were hanging out and Dennis wanted me to sit in an abandoned car with him. He was the "Dad", and leaned over to kiss me. I jumped out of the car and ran home, screaming the whole way "aaaaaaaaaah!"
Our family had never been demonstrative, not even when we kids were little. No hugging, and definitely no kissing.