This was all out of character, during combat. My player was fighting an ape.

Player: *rolls nat 20 when attacking, damage higher than ape’s AC* I SLICE HIM IN HALF! 

DM: His body falls limply to the ground, there is blood everywhere. It pools around your feet, as you stare at the body, fingers still twitching. You killed an innocent creature, but your path is clear.

Player: I cut off its head.

DM: You’re… going to decapitate the ape you just killed.

Player: I cut off its head!

DM: Okay.. you cut off its head, in what appears to be a manic battle rage. Blood spurts from the arteries, spraying your face. The spurting continues as you lift up your trophy, as you realize the wolf and sheep are still nearby. They look horrified. 

Player: I loot the body.

DM: You’re gonna loot the body of the ape you just sliced in half and then decapitated?

Player: … He got in my way. *shrugs*

DM: *sigh* Fleas. You find fleas. Because he is an APE. Do you or do you not eat the fleas?

Player: My intelligence modifier is -3, of course I eat the flea.