Pooping for trains

I think we have reached an incredible milestone with Joshua. He pooped in a public toilet today. Just these past few days, he's started to tell us when he wants to poop. Sometimes in the morning, sometimes at night, sometimes before a bath, or like today, at the dim sum restaurant. We give him a Thomas sticker for every time he poops, and when he has 10 of them on his reward poster, he gets a train, or a ceramic house full of trains. For awhile, it seemed like he really wanted to poop--he'd always say when he was at the toy store: "When I poop, I can get that toy!" I am so proud of him.