Zachary knows to "ng ng" when he sits on the 痰罐. So now he sits at the 痰罐 every morning after had his milk. He also know to tell us "ng ng" after he has 痾左大大 in his nappy, only sometimes when he is in a good mood that he tells us before he "ng ng" in the nappy.
He knows that toilet is for "shu shu" but he doesn't tell us when he needs to "shu shu" yet.