A friend of mine showed me a clip he got off the net. It's a little over six minutes long. It's definitely recent, because of the quality of the animation. It looks like a tribute to Go Nagai, since several of his creations appear. When the clip begins, a series of titles appear in Japanese, with an English translation: "Dynamic Super Robots Mobilize". I also saw a logo for something (a studio?) called Dynamic. We then see a landscape littered with fallen robots. Then an updated version of the Mazinger-Z theme song kicks in and we see the original Mazinger pick up his fist from the ground, strike a pose, and then fire the fist at a horde of monsters, including those that appeared in the "mazinger vs. the Black General" OVA, as well as a few from the Grandizer series. Mazinger is completely trounced, and we see Aphrodite-A has been crucified on the battlefield. Just as they're about to deliver the killing blow, Grand Mazinger appears, flanked by Kotetsu Jeeg, Getter Robo, and others. The scene fades to black, and part 2 begins. A new version of the Grand Mazinger theme song kicks in as well, and the robots destroy the enemy army, rescuing Mazinger. Just as they're about to get to Aphrodite, the Dark General pops up from the ground, and part three begins. The General wrecks Grand Mazinger and the rest. He grabs Aphrodite by the neck, but is stopped by the Getter Robo and Grandizer. Between the two of them, they kill the General, who falls apart to reveal the Emperor of Darkness. Just as everything starts looking hairy again, we see a remake of the opening sequence from the Mazinger-Z TV show, except the robot we see is Mazinkaiser. The clip ends with Mazinkaiser arriving to the battlefield, and a close-up showing us that Koji Kabuto is at the controls. I apologize if I got some of the names wrong. I'm used to the "westernized" translations and may have misspelled some things.