In a mixing bowl, whisk together cake mix and vanilla pudding.
In a separate bowl mix together eggs, oil, milk, and sour cream.
Add wet ingredients into dry ingredients.
Divide batter among 24 cupcake liners. Fill each cupcake liner halfway with batter.
Bake at 350°F for 20 minutes. Remove from oven and let cool.
While the cupcakes are cooling, make the frosting.
In a stand mixer fitted with the whisk attachment, combine butter, powdered sugar, and vanilla. Turn on low and mix until all the powdered sugar is mixed into the butter. Turn on high and whip for 30 seconds until the frosting is light and fluffy.
Frost cupcakes, and top with sprinkles.