The other day I'm trying to work on the computer and kept smelling stinky smells and where is that coming from and Pepper, did you forget to cover up your poop again? So, I go clean the cat box and blame it all on Pepper, and then later come to find out that she's been set up to take the fall.
He comes in, uses the cat box to deposit some very stinky poo, AND THEN LOOKS AT IT AND LEAVES! Oh, I see what's going on now, you know that Pepper gets in trouble for doing this and you've never liked Pepper anyway, so what better way to get back at her than to leave a very smelly reminder of your extreme disdain for her AND GET HER IN TROUBLE AT THE SAME TIME!
Seriously, is it the salmon cat food that's making things stink so much?