The weirdest thing I have seen training was at a dressage clinic with a very well-known instructor. Theinstructor wasin the middle, teaching the rider, but also talking to the observers. The student was very experienced, like PSG, and was on a magnificent horse. At one point during his session, he was directed to ride sitting trot to the corner and then do an extended trot across the diagonal. He did this, really flying across the ring with the instructor talking to the crowd about his trot, when the guy slammed into the far corner wall, still at a full extended trot.
When the astonished instructor asked why he did that, the rider said that nobody had told him to turn.