Beat the pumpkin, sugar, egg, and pumpkin pie spice until it is mixed.
Place the piecrusts on the counter and cut each one into 8 rectangles that measure 3x4 inches. You may need to reroll the scraps to get a total of 16 rectangles.
Spoon the filling into the middle of 8 piecrusts, making sure not to go all the way to the edges.
Gently place the other 8 piecrusts on top of the filling. Use a fork to crimp the edges all the way around.
Use a spatula to gently move the pop tarts to a baking sheet. Bake for 20 minutes. Let them cool completely on a wire rack.
Whisk together the powdered sugar, pumpkin pie spice, and milk. Spread the glaze on top of the pop tarts and top with sprinkles. The glaze will set fast; so make sure you add the sprinkles after glazing each one.