When you ask your toddler to help you decorate the Christmas tree. Sometimes you get this:
But when you run out of non-ornaments which are clearly too gigantic to fit on the tree, and he moves on to helping with the glass balls, you will end up needing this:
And then you will have to move all your breakable ornaments to height of about 4 feet.
And then if you wait a week and buy him his own tree, with his own unbreakable ornaments, you will be rewarded by a) him actually understanding how to decorate his tree and helping, and b) finding out that just because they do not shatter, doesn't mean that they are unbreakable, just pull the string real hard, it will totally break, Mom.