You know how when ladies are really quite pregnant and you can see the little hands and feet of their babies prodding out through the mom's flesh? Well, it's kind of like they're saying "yo", isn't it? ...I just never imagined that I'd ever see one come out grinning with his arms upheld already about to beg "up? up?"
It's from a German childrens' book, some of which my favorite translations are "They kiss each other. Father's penis is growing large." and "Mother and Father lie down on the bed. They put the penis in the vagina. They play with each other. Father and Mother rock to and fro."