Where's the Beef?!

It's in Isabelle's backback and in her hat too.

Let me back up a bit.
Mason randomly throws beef comments out. Beef. Completely random. One day it was "Mommy, there is beef in Isabelle's backpack." Another day it was "There is beef on Isabelle's hat."
Just to clear this up: Isabelle doesn't have beef in either her backback or her hat. She's not from a family who just randomly stashes cuts of cow into their child's belongings.
Yesterday morning he saw the snow on the driveway and just had to go take a few steps in it.
I made the comment "Wow Mason, it's really snowing! Look! you have lots of snow on you!" He just shrugged and climbed in the car with this comment: "It's okay mommy, it all just turns to beef anyway."
How do you not laugh?
Tonight he was making me "tea" in his bathtub and then out of the blue he says, "now do you want a cup of beef?"
I'm not really sure where this comes from. Does he know that it's funny talking beef to his vegetarian mother? I wonder if Auntie Keri has planted beefy thoughts in his head? Her daughter afterall opened the church offering and read the cheque as a letter, "Dear God, thanks for roastbeef!"
Maybe there is something in the water?
I just hope it's not beef....