LOL! I did something similar when I was a kid. I had been riding a really well trained horse named Jerry, chestnut Tbred with a small star and not another speck of white on him. We had just brought my horse, Boozer, home from the track but he had yet to be trained for me. So, unknowing, the barn help put Boozer right next to Jerry, in fact they got confused and put Boozer in Jerry's stall. Boozer was a chestnut Tbred with a small white star and no other white. That night, I go down and saddle Jerry up in the very dim light of the barn. Took him up to the arena and got on him for my lesson. My trainer kept asking me, "Pat, are you sure that's Jerry? Something doesn't seem quite right.". I'd been having a little trouble getting him to trot properly and he didn't want to whoa if I tugged on the reins. He never really did anything totally WRONG he just wasn't quite RIGHT. So, we put it down to the first somewhat cool day after a hot summer. We did some extra trotting and collecting and such before we tried to canter. He acted like he didn't know how to pick up anything but the left lead, which was weird because normally I just had to think about the lead and he got it. Jack, my trainer had Meniere's disease and was feeling a little dizzy that night, so he didn't get up on him like he normally would have. We did ok until it was time to jump. We started with a couple of little X's, like hunter hack jumps. I trotted up them and "Jerry" had a fit, ran out, bucked, bolted, you name it, he told me LOUD and CLEAR that he had no idea what to do with those jumps. Jack finally had a light bulb moment, and had me bring the horse over to him. He lifted "Jerry's" lip to check for a tattoo. Jerry had never run so wasn't tattoo'd, but Boozer had and was. Yep, "Jerry" had a tattoo, I was riding Boozer. Jack almost had a heart attack, if my parents had ever found out that I put the first ride on Boozer at 12 years old, they'd have skinned him alive.