So my boy is over a year old fixed flemish derp (special breed involving cute nuzzles and the most adorable ear flap when he shakes his head). He was fixed in December and before that he was dutiful in using the litter pan. Now...he almost revels in waiting for me to come down to the den and he will will hop into his pen and just poo and pee on the rug we have in there. I do my best to clean up his accidents when they happen, and I even purchased a heavy duty carpet cleaner (I use bunny safe cleaner, no chemicals) still no dice. I think he sees it as a personal challenge to drive his mother insane. How do I get my little stinker to behave himself and start using the pan again?