If it's crap ... We'll tell you
One of the things that Spielberg has gone on record as saying is that most of the special effects in the film are practical. Now that appears to be true. The aliens in the film are puppets. There are three of them, seated on thrones in the kingdom (an Aztec structure that turns out to be a spaceship). And, guess what? They bare a striking resemblance to the little naked bald headed midgets that were seen running around at the end of Close Encounters of the Third Kind. They are indeed supposed to be the ascendants of the Extraterrestrials seen in that film. They are related. Though the film doesn't come right out and say that. A lot of kids haven't even seen Close Encounters. They aren't going to get the joke.