Might just be the only one who has never noticed it, but I fired up Nebula today to have a go at Samurai Shodown II; and when I got to Gen-An's stage (as I have many times before) I noticed clear as day; an ALIEN in their cooking pot!
As you can see, the tail is even in there; there is no doubt in my mind that it is an ALIEN all right, I guess they got away with not crediting 20th Century Fox then!