The embedded video is the Japanese version, as I couldn't embed the Fan Dub.
"A full year after Optimus Prime's resurrection, Galvatron and the Decepticons attack both the planet Cybertron and Earth with the aid of four new members: the six-changing ninja officer Sixshot and the three Headmasters, Destrons whose heads can change into smaller robots in vehicle mode. These include the vampire-like Mindwipe, the gator-like Skullcruncher, and the wolf-like Weirdwolf. The Autobots have some new allies of their own, however; the Trainbots, six Autobots with train alternate modes. Ultra Magnus successfully repels Sixshot's attack, but on Cybertron, the Decepticons are winning, thanks to Wipe's hypnotic abilities putting most of the Autobots, including the Dinobots and Goldbug, to sleep. But then a mysterious starship appears and four Autobot Headmasters (Chromedome, Hardhead, Brainstorm, and Highbrow) emerge to join the battle. Meanwhile, Kup and Spike Witwicky learn that Vector Sigma, the core of Cybertron, has become unstable and is in danger of self-destructing."
Transformers Headmasters Episode 1 (English Fan Dub)
This is surprisingly, good. We Americans never got this version of G1 Transformers. Fitting though, now that every toy has to be a Headmaster - Titanmaster, that is...