I teach a Toddler Time class (several actually). These little munchkins are 18 months to about 3 years old - the potty training phase. Lots of kids come faithfully every week and we get to know each other. My little friends look forward to seeing me, and I adore seeing their faces bouncing through the door (and they literally bounce).
A while ago I was right in the middle of a Toddler Time, doing some fingerplay, when one of my buddies came careening into the circle absolutely exploding with the news he had to share with me. "I'M WEARING SPIDERMAN UNDERPANTS!!" Of course, I knew instantly that he must have finally successfully completed potty training, so I beamed at him and said, "Really!? That's awesome!" Moments like those stick in my head and always bring a smile.