This is truly fascinating to me:
"The image is carved in plaster on a wall in Rome and is dated to somewhere between the 1st and 3rd centuries. It depicts a man looking at a person with the head of a donkey that’s being crucified, and it says, “Alexamenos worshipping God.” It’s believed that this was intended to be mocking the faith of a Christian named Alexamenos."
There was a common misconception in Roman society that Christians were "donkey worshippers" from the misconception that Jews worshipped God in the form of a donkey as described by the Iliad commentator Apion.
I have a theory that since the graffiti was discovered on Palatine Hill, the place where Caligula had bought the building for his imperial palace, that a pagan, Roman general could have possibly done this art.