Now, there's a really good chance everyone on Twitter is "in" on the joke (i.e. please don't harass anyone), but for those who still aren't sure, the answer is decidedly less interesting than a second spacecraft, an extraterrestrial lifeform, or even a specialized selfie stick (that was my hope).
Here's the original image, posted on the ESA's website last Friday, November 7th — a render that shows how the Philae lander would pull off the landing by way of thrusters, harpoons, and a drill in its foot. We don't yet have any pictures from Philae since it landed, but if you're curious, here's an actual Philae selfie taken October 7th and published October 14th. As you can see, the lighting and camera quality is no match for the render.