[SM3DL] W4-4 Easter Egg - Ghost/Alien

Easter Egg in Super Mario 3D Land! I haven't found this. If you finish a Ghost House level (any ghost house) and go to the end and wait at the gate, an alien/ghost creature will appear in the background. You can't see it well in my video, so check it ingame. I'd say it's an alien, because in W1-3 (I think it was that one), you could see an UFO in the sky.