Here’s how the exchange went:
MC: Wow… He’s nine days old today. Can you believe it?
Me: (thinking for a moment) Yeah, wow… he’s peas porridge.
Me: Peas Porridge… you know. Peas porridge hot, peas porridge cold, peas porridge in the pot nine days old. (Beat) Wow, I can’t believe I remembered that.
MC: You better start remembering a lot more when he comes home.
They’re only nine days old once, right? It tickled us at the time, and has been a running joke today.