Transformers: The Headmasters
Following on The Return of Optimus Prime (and in place of The Rebirth), The Headmasters is the first Japanese-exclusive Transformers franchise.

The Transformers' interplanetary travels bring them to planet Darhos, where the Autobots aid desperate prisoners in overthrowing the Decepticons and the planet's decadent ruling class. But that's not all - the key to defeating Scorponok is also hidden on this world!