“Mom, my square-shaped brand-name cereal tastes like O-shaped brand-name cereal!”
“Don’t you mean diamond-shaped, dear?”
“No, Mom. That was just a clever marketing scheme! They’ve been square-shaped all along! And I don’t want them to taste like O-shapes!”
“You should write a letter and deliver it to the Post office!”
Don’t say I didn’t warn you.
I’m sorry, I’ve read this multiple times and I can’t find the pun. Is the joke that there is no joke? That the last line is a total non sequitur? Or did I just miss it?
“Post” is a cereal company. : )