How the Grinch Stole Christmas (1966)
The Grinch is a surly asocial green creature with a heart "two sizes too small" who lives alone in a snowbound cave atop Mt. Crumpit, located above the village of Whoville. He especially hates Christmas and has always been annoyed by the town's Christmas celebrations. One Christmas Eve, he finally decides to stop Christmas Day from coming to Whoville by disguising himself as Santa Claus, his dog Max as a reindeer and, in a reversal of Santa's visit, stealing all presents, decorations, and symbols of Christmas. Once loaded, he plans on dumping the bags of stolen goods. He is noticed by a girl named Cindy Lou Who, but is otherwise undetected.
As the Grinch reaches the icy summit of Mt. Crumpit, ready to dump the bags, he discovers that the citizens of Whoville, despite having no gifts or decorations, have gathered in the middle of town to sing as Christmas Day dawns. Realizing that Christmas means more than just material possessions, the Grinch's heart grows three sizes. He saves the sleigh, returns the presents and the other belongings to the Whos, and joins in the town's Christmas celebration by carving the roast beast, giving Max the first slice.
Credit: Wikipedia