What to think about that? Wished some experts of video material had something to say.
There are many programs out there that can "shop" a photo or vid. Not even difficult any more. Kids do it all the time. That likely was a frame by frame rerendering of the cow figure plucked from the pasture background, with a bit of cloud shape reformed into a ring or saucer shape. http://www.blazemp.com/video_creator_software.htm
for an example.
Or this example of actually doing so:http://www.youtube.com/watch?v=WcIy9O344bI
This capacity to manipulate video images like painting a picture has been around for many years. A lot of hoaxes have been pulled off using it. Putting one person's head on another's body, while that body is doing something funny, or shocking, for instance.
Ten years ago the graphics program I used had a feature that would animate images, including still photos. You could move sections around so that they appeared to be in motion. That cow in the sky was probably pretty easy, though I think I did see one effect that was clever, if not technically difficult. The head and neck appeared to move toward the last few frames. Easy trick.