In a mixture, beat the butter, vanilla and salt until combined. Slowly beat in the confectioners’ sugar and milk until smooth. (You can add more milk or more sugar to make the frosting thicker or thinner, depending on your taste.)
For chocolate frosting, beat cocoa powder into the frosting until combined. Add up to 2 tablespoons more milk to thin out the frosting, if needed.
For the lemon-lime frosting, you can pick lemon zest, lime zest or both. Stir some into the frosting using a spatula. The more you add the brighter and more flavorful it will be.
For strawberry frosting, pulse strawberries in a food process until smooth. Transfer to a saucepan and heat over medium heat until simmering. Stir in granulated sugar to taste. Simmer, stirring occasionally, until reduced by half. Let cool completely. Beat, a spoonful at a time, into the frosting and adding more confectioners’ sugar as needed until smooth.
For mango frosting, puree the mango in a food processor until smooth. Beat, a spoonful at a time, into the frosting and adding more confectioners’ sugar as needed until smooth.
Top frosting with sprinkles and serve with animal crackers.
Tip: You can add food color to any of the frosting recipes to boost or change their color!