There's a thread running right now in Spanish asking this question. I immediately answered (in my verrrrry broken Spanish!) that it's an extra little cake you make for the birthday child so that they don't stick their fingers into the real cake.
All of the other answers that are being written, though, say that it's an extra cake to smash into the birthday person's face.
Is my answer wrong, or the other one, or are they both right?
Thanks!
Hi JGMB you answer was right, thank you so much for your response and thank you for making the effort to write the answer in Spanish you are so nice, Thank You again and Happy Valentines Day, and I want to tell you that any time you need anything you know you have a friend on this forum some times I go to the English one, well I am everywhere here on CC 
, Thank you again and God Bless You 
Frankyia M.
Here in the good old south the tradition is that when a child turns one you have a birthday cake for the party and the extra little cake(Cupcake/ 6 inch cake,etc.) is used just for the birthday baby to make a mess with(and that baby wearing a very large bib helps!) This makes for really cute pictures.
Happy valentines Day to all my fellow CC'ers! 
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