I've got 2: a short one and a long one. First, when I was 16, my friend and I had a long weekend where most of our friends were away on a retreat and my parents were out of town. So it was just us and we were BORED! So... We took my mom's car and we drove from Chicago to Milwaukee. We had lunch, goofed around, and came home that night. No one ever found out. Can't believe my parents never looked at the mileage on the car!
Second, my family was vacationing in the Virgin Islands with our extended family (grandparents 50th anniversary). We heard a rumor that Princess Diana's yacht was moored offshore (This was 1992). My cousin is/was a huge Diana fan, so she was excited by this. On the day before she was leaving, which was a day before everyone else, she said she was too down to go the beach with us. She was such a pain about it, my mom thought we should all tell her that we saw Princess Diana at the beach. We came up with all the details, including the color of her suit. We even enlisted other people staying at the resort. My cousin totally bought it and was kicking herself for not going. The next day after she left, we realized no one told her the truth. Oops! [emoji1]