Bisquick Impossible Pie is a type of pie that uses a mixture of Bisquick baking mix, milk, and eggs to create a unique, crustless pie with a somewhat quiche-like texture. The name "Impossible Pie" comes from the seemingly impossible way the ingredients magically separate into distinct layers during baking, with the denser filling ingredients sinking to the bottom and the lighter Bisquick mixture forming a soft, crust-like layer on top.