I don't know how he did it. I turned my back on Arthur for a moment, and when I looked again, he had taken off his left green rubber boot, put it on his high chair tray, then stuck his bottle into it. I'm not sure if he was pretending to be from the Wild West or the opening of a French opera. So of course I grabbed the camera and started snapping photos.
It wasn't until I had a few that I noticed the potatoe and other food in the tread of his boot. Luckily, there wasn't too much food on his tray, and I reasoned that if he had managed to get the boot on the tray in the first place, that he was probably finished eating anyway.