I have a 2 year old Straight Egyptian Arabian gelding. I got him as a yearling from a barn where the only handling he received was to get his feet done, wormed, and vaccinated. So, I've basically taught him everything from the ground up. He's a VERY smart boy and he's VERY well-behaved. In fact, he's better behaved overall than most of the adults at my barn. He's constantly surprising me.
Well, I've discovered a new trick. A friend and I went put my horse and her yearling Friesian/Saddlebred filly in the arena to "meet" for the first time (my guy was gelded September '10, so they couldn't play before then) and my turkey of a baby started free-longing himself. No kidding I unhooked the leadrope, walked away, and he followed and proceeded to longe in a very nice circle around me. Now, when he longes, he's fast. I mean he runs as fast as his little legs will carry him. We couldn't believe our eyes. I just stood there and he ran circles around me. I walked out of his circle and he continued "longeing". When the filly came into the arena, he tried to push her into running in circles with him.
I guess this is a true testament to his quality of training and how intelligent he is.