After the clapping I kept the camera rolling and managed to capture Corgan signing "more"! :) He's doing it all of the time now and even did it a couple of times today without any prompting AND for something he wanted "more" of that wasn't even food. He also signs "puppy" (well, "dog", but I call it puppy when I do it), but that's pretty rare.
And here's another "Corgan Clapping" video, but my favorite part of this one is Annabelle's line at the end. :)