At first glance, this episode is wonderful. Funny, achingly sad, and adorable all at once. But look a little deeper and you'll find that What Is and What Should Never Be shows a level of sophistication, acting, series and character continuity, and polish, that will blow you away.<br /><br />Jensen Ackles knocked this one out of the park. Though he always does an exceptional job, he really took it up a notch this time. Never an off moment in the whole show. I have heard him referred to as a subtle actor before, and I think that comes through in this episode. The facial expressions, the gestures and movements are all spot on. You don't have to wonder how his character is feeling; it's written right there on his face, and in his eyes, for all to see. He's heartbreakingly sincere. Spectacular. Jared Padalecki also did an excellent job in this one.<br /><br />A definite must see for newcomers and regulars alike.