One thing you need to be wary of with these sorts of records is that the person doing the engraving and the printing may very well not be the person who saw the phenominon; indeed, he may not have even spoken to him directly, much less at length.

See, by way of example, renderings of elephants and other even more exotic animals by period artists.

They were absolutly not meant to be a joke. These kind of sightings were mentioned on a fairly regular basis in various sources upto the 18th century. I researched almanacs which mentioned not only occurences similar to this one, but would also mention dragon appearances or stories of witchcraft alongside information about royal succession or war efforts. These type of events were mostly attributed to either God or the Devil. They were mostly secondhand accounts and refered to sightings in a distant city. When this is the case, it's very hard to determine if these sightings were inspired by actual events. However, there are also sightings mentioned within almanacs produced and distributed within the region where these sightings were said to have taken place. In this instance, you could argue that these stories were inspired by some sort of actual natural phenomenon. However, it's also entirely possible that they were completely fictional and were made believable through oral tradition. For example, some people would read this and retell it as if they actually witnessed it or know someone who did.