television series in Japan, immediately following Season Three.
In Japan, where the Transformers phenomenon never died out as it did in America, the Transformers continuity took a remarkably different turn after the third season of the TV show. The movie did not actually happen (and Optimus Prime's absense from the show was explained in an OAV called Scramble City), and a new Transformers anime series commenced the next year. Called Headmasters, this series continued the Transformers adventure after the third season, ignoring the three-part Rebirth episode altogether.
In Headmasters, rival groups of Cybertron (Autobot) and Destron (Decepticon) Transformers from a long-lost Transformer colony on planet Master returned to Cybertron (called "Seibertron" to distinguish it from their name for the Autobots) just in time to get caught up in the battle between the two factions. Planet Master, it seems, is a world of smaller (human-sized) robots, who built larger bodies called transtectors for themselves to aid in their survival and exploration. The robots can trade "heads" with each other (swapping transtector vehicle/bodies), and have other special powers. Thus in the Japanese version, Headmasters are smaller robots, not enhanced humans...at least until Masterforce comes along.
Some interesting things happen--in the first episode, we get to see Trypticon defeated by...Daniel Witwicky and Wheelie. Over the course of the show, Blaster and Soundwave die and return as newer toy versions of themselves, Optimus Prime dies--again--and Cybertron and Mars are destroyed. Sixshot kills Ultra Magnus, and is subsequently befriended by Daniel. Galvatron has a fiendish plan to turn the Earth into a new body for himself, Unicron-style...and he cannot be allowed to succeed.
Headmasters is often decried by Transformers fans as even more of a toy commercial than Rebirth, showcasing as it does Headmasters, Targetmasters, Sixshot, Punch/Counterpunch, Fortress Maximus, Scorponok, the Horrorcons, Transformer Clones, Battle Beasts, and many others. It also spotlights some toys not seen on this side of the Pacific, such as the Trainbots, a combiner made up of five different train cars. Nonetheless, it did maintain much of the flavor of the original TV show in terms of animation style, flipping-logo scene transition/musical sting effects, and so forth, and it at least gave the new toys more screen time than Rebirth.
Recently, Headmasters has been broadcast on cable TV in a horribly dubbed version (in which, among other things, Spike Witwicky is referred to as "Sparkle"). This version can be found as downloadable video files on several TransFandom web sites. Warning: viewing this dub can result in loss of SAN points.