When Professor Pain talks about how the German language is weird he mentions that pencil is called Kugelschreiber in German. Kugelschreiber is ballpoint pen and not pencil. Kugel = Ball.
In the scene where Delia and Melinda bring Bob the dog to Cesar Milan the book posters in the background show a much older Cesar Milan while the Cesar Milan in this episode is much younger and with still brown hair.