By far, my favorite Christmas special is "Merry Christmas, Charlie Brown." It's the story of the Peanuts gang trying to put a Christmas pageant together and Charlie Brown is trying to figure out the true meaning of the season. Charlie gets asked to direct the pageant, where his every move is questioned and his instructions go unheeded. He realizes in all of this that something is missing in all of the craziness surrounding the event.
Enter Linus. He goes to center stage and proceeds to recite a portion of Luke 2 - the Christmas Story. After finishing his recitation, he turns to Charlie Brown and says "That's what Christmas is all about, Charlie Brown" that clip of the movie is below.