Pineapple Pretzel Salad

1 cup crushed pretzels 
1/2 cup butter, melted  
1/2 (8 ounce) package cream cheese 
1/2 cup white sugar 
1/2 (8 ounce) container frozen whipped topping, thawed
1 (20 ounce) can crushed pineapple 

Preheat oven to 350 degrees. Place crushed pretzels in the bottom of a 9x13 inch baking dish. Pour melted butter carefully over top. Bake in preheated oven 10 minutes. Cream together cream cheese and sugar. Fold in whipped topping and pineapple. Spread over cooled crust. Chill until serving.