Four Warriors From Outer Space.
The Mystery of Planet Master.
Behold the Birth of Double Prime.

The first three episodes were a 3-part story, so will comment on all 3 together.

Since the US 3-part story 'Rebirth' is not included in the JP Gen1 cartoon universe, this story takes place after the episode 'The Return of Optimus Prime' (the US title). As such, the Matrix is empty, and it seems that the Decepticons are taking advantage of the chaos, by trying to capture Cybertron and Vector Sigma.

For some reason, the Decepticon Headmasters are already around, but the Autobot ones only just arrived in this story. And very little is explained, other than that they have (suddenly) returned after 4 million years.

We also don't know much about the planet 'Athenia', or where it is, despite it being implied that they have had the base for ages, and is of strategic importance.

A fair bit of fighting goes on throughout this story, which pads out the story a fair bit, and we get to see new characters being shown off to the audience. We also see the end of Soundwave and Blaster, who fight to the death, killing each other.

Some other things that bothered me:
- The poor timing the writers had with the plot. We have Optimus going to Cybertron and spends about 2 whole episodes slooooowly making his way to Vector Sigma, only to have everyone one else show up within minutes of their journey.
- Galvatron is closer to Vector Sigma when it exploded, but Optimus Prime dies, and he seems quite happy to sacrifice himself.
- The Autobots in a later episode can easily rebuild a 'dead' Blaster, but don't do anything with rebuilding Optimus.
- Hot Rod becomes Rodimus again, and seems to be a big deal as if it is the first time.
- Trypticon tries to walk across a tiny suspension bridge, and naturally it breaks.
- The Autobot Headmasters tell Galvatron their names when he demanded it.
- Chromedome says he's the leader of the Autobot Headmasters in episode 1, but Fortress (Cerebros) says he is, in episode 2.
- In episode 2 the Autobots don't know if the Fortress Maximus (battleship) is friend or foe, despite arriving in the previous episode and having 4 Autobots fly out and fight the Decepticons.
- Optimus goes to to Vector Sigma without the Matrix, which he needs, so now a whole episode needs to be wasted looking for it. And why wouldn't it be kept on him instead of being hidden in the floor of some building, and not tell anyone where it is?

And Trains that can fly across the universe??? Who comes up with this crazy s...stuff?