“Happy Birthday” Cupcake Boxes. Why give everyone just a slice of cake when they could have they're own individual cupcake instead? Hand these out to all your birthday party guests to give them a sweet treat to remember your celebration by. Printed with colorful cupcakes, each “Happy Birthday” Cupcake Box includes a 3" cellophane window in the lid. Cardboard. 4 1/2" Simple assembly required.