Once, when I was desperate to practice but had no time after work, I played my viola beside the garbage dump of a hospital during my lunch break. People walked by but thankfully didn't say anything. I do hope that the people in the hospital enjoyed the Tchaikovsky!
Went twice the speed during an orchestra performance. Lead the section astray. The conductor began counting out loud to get everyone else back on track. Eek!
I play on an eBay Yitamusic viola. The viola has my last name written in Chinese on the body of the instrument, near the tailpiece. It's a tiny scribble, I didn't notice it until this year. Coincidence, or fate???