Like milagros, mine go back to childhood. I was good friends with a girl who lived two houses down. She was the skinny tom boy type girl. Her father was a smallish man, and the wife an extremely large woman. We were playing marbles on her living room floor when her mother stormed into the room and started yelling at her for not doing the dishes (she and her brother had alternating days apparently). The mom told me to hold her wrists. Then she straddled her waist easily pinning her to the floor. I had no idea what was about to happen, when the mom started tickling her ribs. She exploded in laughter and I could feel her pull hard to try to get her hands down to protect her sides. The mom was taunting her and just kept tickling. It was the spark that lit the fire for me. I really enjoyed holding her wrists down and it wasn't very hard because she wasn't strong to begin with. But the tickling seemed to weaken her even more. I held on tight as her mom used her pudgy fingers to work over her ribs and then when she went into her armpits the laughter poured out. The mom laughing the entire time as well. So it didn't feel cruel in any way, but the laughter filled the room. In my mind it seemed like it lasted for a long time, but the reality is probably it was only about 10 minutes. But those 10 minutes have filled my memories decades later and I am convinced that event fueled my adulthood interests.