Litter Box problem

[Uabassoon]

Lately Tuna has decided that the proper way to use the litterbox is to stick his bum out of the door and poop on the floor. He always goes to the litterbox, he just has the wrong end sticking out. How can we get him to stick his bum in the litterbox instead of out?

I also wanted to include this random picture of Tuna in his halloween costume.