In a large bowl (preferably a chilled metal bowl), fold together the whipped topping and the sweetened condensed milk.
Gently crumble or rough chop the cupcakes and stir them and the sprinkles into the creamy mixture.
Immediately pour into a 8-9" loaf pan. Top with additional sprinkles, if desired, and cover with foil. Freeze for 4-5 hours, or overnight.
When ready to serve, remove from the freezer, scoop, and serve immediately.