Why "Eat More Chikin" is funny...

Pragmatics is so NOT my son's strong suit. Expressive language & pragmatics are two areas where he is seriously lagging.  It is almost funny when he tells a joke. He laughs because he knows it's supposed to be funny but literal boy doesn't get the joke.  Sometimes it's not worth explaining.

We went to an event where Chick-fil-a had a booth.  They gave my son a miniature of their cow mascot.  The cow holds a sign that says "Eat More Chikin". So the conversation goes like this...

Blue "This cow is cute, but why is it holding a mispelled sign about chicken."
Momzilla (driving) "It's a joke Blue, but do you get it?"
Blue "Hmm, no."
Momzilla "Where does chicken come from?"
Blue "Chickens!"
Momzilla "What is made from cows?"
Blue "Milk!"
Momzilla "Cows make the milk, not milk is made from cows.  Okay let's try this what is McDonalds famous for?" (thinking of the billions of burgers sold)
Blue "Chicken McNuggets"
Momzilla (okay I'll try something else) "What is BURGER King famous for?"
Blue "umm, burgers?"
Momzilla "Right!  Now where do burgers come from?"
Blue "Pigs"
Momzilla "No.  Pork comes from pigs, and so do some hot dogs & sausage. Try again. Where do burgers come from?"
Blue "Cows?"
Momzilla "Right! Now why do you think the cows have a sign that says "Eat More Chikin"?"
Blue "Because chicken is good."
Momzilla "Okay let's try this, if the people eat only chicken, will they have room left to eat burgers?"
Blue "I guess not."
Momzilla "So if people don't eat burgers, what will happen to the cows?"
Blue "I don't know"
Momzilla "No need for beef, no need for cows to be slaughtered. Now what would be the same kind of funny for Burger King to have a mascot?"
Blue (really excited now) "A chicken with a sign "eat more beef"!!?!"
Momzilla "Exactly!  Now why is the Chick-fil-a cow funny?"
Blue "Because if you eat more chicken they won't turn cows into burgers."
Momzilla "Nice job dude."

The above conversation took about 20 minutes.  He understood that the cows & chickens aren't alive when he eats beef or poultry.  A few minutes later...

Blue "Hey mom?"
Momzilla "What bud?"
Blue "Do cows die when they make milk?"
Momzilla "No bud. They really make milk as mommy milk for baby cows.  The extra milk is treated so humans can drink it."
Blue "Are you sure?"
(My cousin's wife is breastfeeding their 2 month old daughter so he's a bit familiar with the concept as much as a 7 year old should be.  He knows he was given "Mommy Milk" when he was a baby since it was what was best for him.  We still laugh how my (now late) father refused to call it breast milk, it was always Frozen Mom Milk. )
Momzilla "What does Aunt C do after she feeds the baby mom milk? "
Blue "she burps the baby"
Momzilla "Is Aunt C okay after feeding baby?"
Blue "Yes"
Momzilla "Well cows are okay after they make milk whether it's for their baby calf or for the milk factory.  Just like Aunt C.  Okay?"
Blue "Okay.  I like my new cow. I'll call him George."
Momzilla "You know cows are girls and bulls are boys right?"
Blue "I'm still calling the cow George"

Whatever...