This lie has been bugging me since I was ten years old, so I might as well get it off my chest:

I was in year five (fifth grade for you Americans), and it was afternoon recess. I was in the classroom, though I probably shouldn't have been, and another girl and I were jumping from desk to desk.  The desks were in rows and we were jumping from row to row.   I went around the classroom twice without touching the floor. On my third circuit, I misjudged the distance between two rows and missed the desk, smashing my shin on the metal tray holder that protruded from the underside of the desk. My shin was gashed open, and bleeding everywhere. I sat on the floor staring at the wound and making peculiar gurgling noises. The girl who had been with me ran and got the nurse, who came in and demanded to know what had happened. I knew I'd get into big trouble if I told the truth, so I thought fast, and the best my slightly hysterical mind could produce was "I was standing on the desk reaching up to the window sill to get my pencil case, and the desk was wobbly and I fell...."

She bought it! Though by this time I was gazing tranfixed at the huge hole in my leg and the blood gushing down my shin, and didn't really care whether she believed me or not. Anyway, I missed PE because I had to go the doctor for stitches. Needless to say, the doctor, my mother and my father all heard the story. And all believed it!  I still have a scar on my shin, and every time I look at it, I marvel at why they never thought to wonder why I needed my pencil case in the last three minutes before PE, and why it was on the window sill when I always kept it in my desk which was on the other side of the classroom.