Preheat oven to 350°F (175°C). Line two muffin pans with cupcake liners.
Whisk together flour, baking powder, and salt in a bowl.
In another bowl, cream the softened butter with sugar until light and fluffy. Add eggs one at a time, mixing well after each addition, then stir in vanilla extract.
Gradually add dry ingredients alternately with milk until just combined.
Fill cupcake liners two-thirds full and bake for 18-22 minutes until a toothpick comes out clean. Cool in pans for 5-10 minutes before transferring to a wire rack.
For frosting, beat softened butter until fluffy; gradually mix in powdered sugar and cream/milk until smooth. Divide and color frosting as desired.
Pipe white frosting onto cooled cupcakes, then add colored irises and candy eyeballs on top.