Cute! I have one like that, as soon as he's loose in the indoor, it's over to the mirror! Loves himself!
It's almost like he's playing Peek-a-boo with himself. Watch when he gets all the way to the left of the mirror, he bounces back to it, like hey, they you are!
Well my mare is now doing this in the indoor arena. Trots over to the mirror and just stares at herself!