I have a similar problem with my dog but he wee's by the litter tray, the thing to do is keep an eye on him and tell him no and stop/move your dog to where he is alowed to go to the toilet outside and give loads of praise when he's doing it in the right place you have to reinforce the training that you started when he was a puppy toilet training he will soon get the idea, I think they just get confused that kitty is allowed to go inside in this tray thing so that must mean that they are allowed to go inside to and we have to get it in to there cute little heads that this is not the case. as for the removing poo from the tray that only happened once with our dog he was told no/drop and he hasn't touched it since thankgod! Good luck. :-)