There is no real potty training. You can catch it every time in it's life and it will not be trained.
Catching it only gives it happy points which is just fine by me but it will never find the potty by it's self.
The closest thing to potty training or rather cleaning by it's self is on the Entamas and Uratamas where you can get the Robot Butler to clean up after your tama.
it goes as mant times when you get 5 traing points or more it get wiggley lines around it and then you push toilet you should see it sitting on a potty or duck thing