Oh gosh - in recent memory that has GOT to be the time we took Gracie and Allie for a lesson with my dressage instructor Ann.
We had tied the girls up to the float and started to tack up when a horse in a yard on the other side of the hedge chucked a bit of a spaz. BOTH of our girls pulled back and got loose - they charged down toward the arena and pranced their way around Ann's property while I ran to the front gate to close it and Natalie tried (in vain) to catch them. Allie even ducked under a strand of electric fence! The poor girl who had been having her lesson before us had to get off her horse and we were mortified.
We eventually caught them, tacked up and had our lessons (they went really well!). The girl whose lesson was so rudely interrupted was quite good about it - it turns out her gelding was the one who pulled back and charged up the driveway a few months before as we were driving in for a lesson - I had caught him for her and so she understood why our silly mares acted so stupidly! Ann thought it was funny and commented that they just needed to let some steam off.