Since then, numerous outlets are reporting that the image appeared over the weekend. Unless there is more than of these images in the Borgo, this simply is not true; I saw it several months back (in late September, if memory serves properly).
I'm certain I took a picture of it when I saw it, but I cannot manage to find it. I'll keep looking, though, and if I do find it I'll pass on the time stamp to give at least some indication of how long it may have been up. Why it's taken this long for the media to notice is quite beyond me.
Father Dwight Longenecker is presently in Rome and has seen the image, as well. He offers a few reflections on the notion of a papal superhero:
Is Pope Francis a superhero? First we have to define a hero. The classic hero is one who goes on the hero’s quest. He or she leaves their ordinary world of comfort and security to set out on a great adventure. Once on that journey they meet allies and enemies, they encounter great dangers and take huge risks. They eventually overcome the dragon, the beasts, the villains and the darkness not only to defeat evil and win the treasure and defeat the prize, but also to become wise and pure and therefore become a hero.I've never been much of a superhero/comic book fan, but I do like wearing capes and am happy that superheroes wear them. The Incredibles may not like them, but only because theirs aren't detachable from their costumes (mine are).
Since “super” means “above” then a superhero is one who goes on the hero’s quest with strength from above. This strength we call “grace”. So is Pope Francis a superhero? By all means. Yes! But so is every Christian who wins the prize and overcomes evil in their lives. All the saints are superheroes and all the Christians who have heard the call to truly follow Christ are on the heroic quest. We’re a work in progress. We’ve heard the call and set out on the great adventure of following Christ, until at last we overcome the world and enter into the realm of the superheroes [more].
Update: It seems that I did not take a picture of the image, but the Vatican Insider has provided the name of the artist.