skipper's circus tricks

When I bought the yella horse I was aware that he had begun training to be a show/circus type horse for a Western riding display, for county shows etc. Mostly he doesn't need to use these tricks, and I hope one day he will forget them...but I now doubt that's going to happen! We have seen evidence of his nodding, stealing things from your pocket, stealing hair bobbles, stealing paper from your hand (all taught) but until this morning I had not seen his most scary trick. His trainer told us he would rear, to order. I particularly desired neither to see this demonstrated, nor to learn the cue for it. Its a very dangerous habit in a horse, and never to be encouraged. Circus horses do it I know, but not my Skipper. For almost a year now I have seen no signs of it, BUT this morning I turned him out, as usual, and I did something I don't normally do - I'm not telling what it was, but his tiny brain clicked into gear, and he gave it a moment of consideration, and he then politely and in an organised manner stood up on his hind legs!!! I nearly laid an egg. He dropped back to all four feet, looked at me to see if that had been the required performance, and then wandered off to eat his grassy breakfast. My heart was beating like a drum, I can tell you, because a horse of 16 hh striking you with a rearing forefoot (and this does happen) can kill you. I know exactly what action was the cue, but still can't believe it happened. I now can't decide whether to check this really happened by trying again, or never doing what I did again in his presence. Just goes to show that horses have a long and accurate memory for their training, and when a horse has come to you from someone else you never know what they might have learned. Scary.