I don't know about number 1, but my dog DOES practical jokes. Eg. If he is excited or he's bored and wants to play, he will pick up a toy, look at me in the eye, and start jumping or running away from me as I move. And then I just 'pretend' to be chasing him and he will run, freeze, run, freeze... Until I tell them to come and to give the toy to me. He enjoys it very much. I can swear that he laughs the whole time. In contrary to public perception, GSDs R silly like that. As you said, yours is scary smart. He knows how to entertain.