Preheat oven to 180 degrees C. Grease a 23x33cm cake tin.
In a small bowl, combine the biscuit crumbs and butter. Press into the bottom of the prepared cake tin. Pour the condensed milk over the crumbs as evenly as possible. Sprinkle the Smarties, coconut and nuts over the milk, press in lightly.
Bake in the preheated oven for 15 to 20 minutes. Cool before cutting into bars.