Too many nature/dinosaur books, or a certain parent letting the kid watch Zombie Lego on YouTube?
The scene: Saturday morning lie-in in bed, father wondering whether anyone'll notice if he drifts off again, mother getting ready to jab father in the ribs if he does, son with stuffed Ikea cats Didi and Joey."Joey's killed Didi"
Concerned mom: "why's Joey killed Didi?"
"Joey's not dead. Didi's dead. Joey killed him."
Concerned mother: "yes but why?"
"Joey's going to eat Didi."
*Joey pounces on Didi* *nom* *nom* *nom*