Heat the oven to 350 degrees and line a muffin tin with four paper liners.
In a mixing bowl, stir together the pumpkin puree, sugar, egg, baking soda, and cinnamon until smooth.
Add the flour and mix just until no dry streaks remain.
Spoon batter into each liner until it is about halfway full.
In a small bowl, beat the cream cheese and powdered sugar until creamy.
Drop a spoonful of the cream cheese mixture into the center of each muffin.
Cover the filling with the remaining batter.
Bake for 20 to 25 minutes, until a toothpick inserted into the muffin edge comes out clean.
Let the muffins cool completely in the tin.
Use the black decorating icing to draw jack-o'-lantern faces on the tops.