Yes, it's a dick. And it was put there for a reason. No one really knows, although a popular theory is that it's a reference to a former work of Ishida's, a webcomic called The Penisman. I've never found a version of Penisman in English though, so I couldn't check it out myself. But, the main character is a literal dick, so it's within the realm of possibility for Ishida to just throw this in there. If he was trying to tell us something else, I'm sure people would have just picked up on it by now.