Copyright issues would come into play if WordPress tried to brand itself along with the Calvin character. Nobody here at WordPress, nor myself, claimed to have created the Calvin character.
As was actually noted, there are thousands of Calvin images on vehicles where Calvin is urinating on an (insert corporate logo here) .
I doubt if anyone has permission to use the Calvin image in this way, and, I might add, people get paid to create and install those graphics. So, before somebody has a damn cow about "copyright enfringement," make sure that there actually is copyright infringement.
All of the non-standard WordPress logos were done by me so far. I took the official WordPress logo, without anybody's permission, and did what I pleased with it. I then submitted them all to WordPress devs for them to use or not use as they saw fit.
So, if anybody wishes to bring legal action against me, please email me and I will send you all of my contact information to make it easy for your legal team to begin the process of suing me.
Otherwise, just go about your business and don't get your family jewels all twisted into a knot about something so damn trivial.