One Black Personalized Onesie. Choose from 6, 12, 18, or 24 month sizes. Celebrate a special first birthday, thrill a mother-to-be, or complete your little one's outfit with a Black Personalized Onesie! Simply enter the child's name in the 1st Line of the Product Options, and we'll print it on the onesie. Be sure to browse our fantastic selection of themed tableware and decorations in our Baby Shower Supplies and 1st Birthday Party Supplies.