Possibly not internal -- if you are holding a camera up to a window with a dark background, and the camera is lit, you might get something like this. (Pic taken holding camera very close to the glass and holding a flashlight above it.) The little arc at the bottom is a reflection of the illuminated barrel (terminology?) of the lens.
I'll edit this post after it gets dark here, when I can try with a darker background, if the results are better I'll add another pic.
That still leaves issues with why the details of the reflected camera bit would not be more consistent, maybe there is some control of that by tilting the camera, reflecting off of distorted bits of glass, or even messing about with sticking stuff on the camera to alter the reflection, going for an intended new effect or just a random something new.
EDIT AS PROMISED: Though I'm no longer thinking this is plausible as an explanation, due ot how the UFO moves about frame when the camera shakes, while when I shook my camera the reflection of the camera stayed in place I did go back tonight and try with a night background -- shooting the reflection of the camera in a window. It looks closer, though too many rings and I'd need a softer light, and would need to control for some errant light where I don't want it... and my camera has the disadvantage that my fingers are unfortunately positioned! But with enough time and effort and a similar camera to the one Mr. Yalman had maybe I could get pretty close...