Preheat the oven to 350°F. In a bowl, combine the crushed pretzels, butter and sugar. Press the mixture into an ungreased 13x9-inch baking dish. Bake for 10 minutes. Cool on a wire rack.
In a small bowl, beat the whipped topping, cream cheese and sugar until smooth. Spread the filling over the pretzel crust. Refrigerate until chilled.
Dissolve the gelatin in boiling water in a large bowl. Stir in the strawberries, then chill the strawberry Jell-O topping in the fridge.
After the strawberry Jell-O topping has chilled in the fridge until partially set, carefully spoon it over the filling in the 13x9-inch dish. Chill the pretzel salad until firm, for four to six hours.
Cut the strawberry pretzel salad into squares. Serve with additional whipped topping and additional pretzels if desired.
