Douglas, also known as "Daggeles", is a mouse with a sense of humor.
In this case, toilet humor.
If your first language is not English, you might not get this image. Should this be the case, Douglas wishes it to be known that this image was not his idea and that he distances himself from its content.
"Daggeles", in fact, is the way a German would probably spell the word Douglas if he heard it for the first time. Daggeles loves a she-mouse, Josephine.