Prepare cake mix according to package directions for cupcakes by combining the cake mix, water, vegetable oil, and eggs. Bake cupcakes for 14-19 minutes and let cool.
To make the frosting, beat butter until creamy.
Add powdered sugar, vanilla, heavy cream and salt and mix together with a hand mixer until well combined.
Add green food coloring until desired color is reached.
Spread or pipe frosting on top of each cupcake.
Cut each AirHeads Extreme candy in half and place on top of each cupcake to create an arch.
Place two mini marshmallows on each end of the rainbow.
To make the pot of gold, pipe a small amount of frosting onto the wide end of each Rolo, then press into gold sprinkles until all the frosting is covered. Place on the cupcake.