You scared my with that title! I was expecting to find a video of a horse being flipped.
At the horse camp I used to work at, one of the trail guides had all her student's convinced that her horse could do a back flip on command. She told them that all she had to do was lift the reins and say "Back FLIP!" in a very high pitched voice. She totally had them convinced. So, whenever they were on trail ride she rode in the back as the tail horse and whenever the kids weren't looking she'd say "Back FLIP!" and all the kids would turn around to see and she's just say, "Aw, too bad, you guys just missed it!" They eventually figured out it was a joke but she had them going for a couple days. It became an inside joke for the counselors and trail guides