like the others i haven't heard of this either. 'smash cakes' seem to be the norm.
the biggest 'tradition' that i hate is the "birthday spanking." my immediate family never did it, but one summer, i was at m grandmother's for my birthday (we happened to be staying there between houses (one sold before the next was available). my aunt (who is crazy) was also there at the time, and she said and did a lot of nasty things to us.
usually, my mom or dad would step in--for example, once i didn't want to eat boiled spinach, and my aunt said that if i didn't finish it, i'd have to take all of my meals on the floor like the dog,, and then proceeded to put my plate on the floor with the dog--and my parents said no.
but for some reason, they didn't say no to the spanking. this might be because the whole family was there--all 4 of my father's siblings, their SOs and children, and apparently they ALL did this at every child's party. (prior to this, we lived far away and so we always had family parties that were the immediate family, no GPs, Aunts, uncles, cousins, etc). so they allowed it.
i was humiliated and mortified. i really dislike that crazy aunt too. and her children are seriously f-ed up.