Layer one: Melt the butter in the pan. Mix pretzels with sugar and sprinkle over melted butter. Bake at 425 degrees for 5 minutes.
Layer Two: Combine the cream cheese, sugar, Coolwhip, and drained pineapple. Mix and spread over pretzel crust.
Layer Three: Dissolve Jell-O in hot water. Add cold water and stir to mix. Add frozen fruit. Pour carefully over 2nd layer. Chill to set.