I saw the last half of this movie on SciFi and then a few hours later, I saw the beginning when they replayed it. If I had seen it from the beginning, I would have been a lot more disappointed, because the opening sequence was amazing, and sadly, the rest of the film didn't quite measure up. But the opening? Great CGI effects giving way to traditional animation (of cave drawings) that gave us a taste of the backstory, with fun, appropriately theramin-heavy music - it could have been the opening to a theatrical film, it was just that good! I can tell what the director/writers/producers were going for with the rest of the film, with the over-the-top plot, characters, and humorous lines and references to classic 50s sci- fi schlock. But it just didn't quite come off. And for the hour that I saw of it, they could have benefited from a whole lot more mammoth, since that IS the title. Oh well. I bet the creators do better next time.
