Comma, comma, come ON! (really?!)

What is it about poop that Olivia has found so funny lately? First she's pooping her flute, now this:
We've been engaging in a LOT of baby talk these days, er...talking about the new baby, not talking LIKE babies. Can you imagine? The three of us around the dinner table: "O-wiv-ee-a, want more pot woast?" It makes me uncomfortable even thinking about it. Strike the image from your mind...immediately.
Olivia has gotten to feel Baby Girl kicking and often puts her hand on my belly, hoping to catch some "gymnastics." We visit the baby's room, discuss what she might look like (Funny thing - the other day Pie saw a picture of a baby in a frame and asked if it was __________.), refer to her by her  99%-sure name, and talk about what life will be like when she arrives, specifically the activities the girls will get to do together.
Yesterday, I was sitting in a reclining position and Olivia had her hand on my stomach, waiting patiently for Baby's signs of life. It was then she asked me if __________ could sit. I told her, no, our baby doesn't know how to do anything yet. In fact, "when ___________ is born, the only things she'll know how to do will be eat, poop, and cry."
Olivia hesitated. "Eat...poop? Eat poop?!"
Realizing I had been unclear, I quickly corrected, using my fingers to count off the things she would do, "Eat. Poop. Cry."
"Eat poop!"
"No silly! Yuck! We don't eat poop! Ick!"
"Eat poop. That's yucky." But then again, "Eat poop and cry!"
So, clearly, she understood, but couldn't let it go. I guess the visual of her baby sister eating poop (and crying - who wouldn't?!) was just too funny to let go.
I tried reversing the order and even added "sleep" to the list (cry, poop, sleep and eat) but, no, "eat poop" it will be for a while...
Again, what's with the 9-year-old boy hi-jacking my kid?!
And, is it too early to teach her about commas?