Heat the oven to 400°F. Line a 10×15-inch rimmed baking sheet with foil and spray with cooking spray. Arrange the saltines in a single layer, edges touching.Melt the butter and brown sugar in a saucepan over medium heat. Bring to a boil and boil for 3 minutes without stirring much, until thickened. Stir in the vanilla.Pour the toffee evenly over the crackers and spread quickly to cover.Bake 5 to 6 minutes, until the toffee is bubbling all over.Remove from the oven and sprinkle the chocolate chips on top. Let sit 3 minutes, then spread smooth.Sprinkle with chopped pecans and red and green sprinkles, pressing lightly.Refrigerate 1 hour until firm, then break into pieces.