While cake is baking, simmer crushed pineapple with sugar.
When cake is done, immediately remove from oven and put holes in cake top using a fork.
Pour pineapple over top. Let cool on rack.
Mix vanilla pudding with ½ cup coconut and spread over pineapple.
Ice cake with Cool Whip. Sprinkle walnuts and remaining ½ cup coconut over the top and refrigerate at least 24 hours (48 hours is even better, to allow flavors to mingle).