Place a large skillet over medium-high heat.

Whisk the eggs in a large mixing bowl until the yolks and whites are evenly combined. Stir in the milk, pumpkin purée, and vanilla extract. In a separate mixing bowl stir together the pancake mix, granulated sugar, and pumpkin pie spice. Slowly add the dry ingredients to the wet ingredients about 1/2 cup at a time, stirring them with a wooden spoon just until combined (don't overmix - the batter should be quite lumpy).

When the skillet is hot, lightly grease the surface with butter. Gently ladle the pancake batter onto the griddle. When bubbles begin to set around the edges and the skillet-side is golden, gently flip the pancakes. Continue to cook 2-3 minutes longer until the pancake is cooked through. Serve immediately.