Forever Is A Long Time Coming

Perceptor, Blaster, Wreck-Gar and Blurr are led out to an ancient asteroid belt and none of them have any idea why they're out to see a bunch of old rocks, except for Perceptor, who explains that a peculiar energy is emanating from them. Chrono energy. The force of time itself! He also mentions that he brought the others along for protection, said conveniently just as lasers are shot from an asteroid and Sharkticons start approaching!
 

While Blaster contacts Rodimus Prime for reinforcements, he ejects Ramhorn to plough through some of the Quintesson lackeys while Wreck-Gar and Blurr blow them up real good, with Rewind providing some additional cover. Perceptor, meanwhile, heads down to the asteroid himself to see what's going on, and discovers something insidious going down.

"Set the coordinates at minus eleven million years. At my signal, open the time window and begin the retrieval."

"No!"
 

The Quintesson monitoring the time window reminds his crew that it can only stay open for four hundred macro seconds, and makes use of the "energy hook" to retrieve what they want. While Perceptor utters a few typical "no!"s and an "it's impossible" or two, the other Autobots are chased into the time window by a few Quintesson warships, shooting Perceptor unconscious in the process.

Rodimus and Superion arrive on the scene and take down the Quintesson warships, but not before they damage the time window, forcing the tentacle-bearing ninnies to retreat against the wishes of the supervisor who says they shouldn't leave the time window open with no one to shut it down. Rodimus and the Aerialbots check up on Perceptor, who manages to utter "through the time window" before lapsing back into unconsciousness.
 

As this occurs, an unknown individual appears before the Autobots! Using incredible senses of deduction, Rodimus suggests he came from the time window. Hurf.

Rewind, on the other side of the window, finds the place they're in quite familiar, but has to beat a retreat with the others after a searchlight is beamed on them and guns start a firing. As they flee, a Guardian is dispatched to hunt them down, a robot from the earliest days of Cybertron!

It stops them in their tracks, eventually, forcing them to stand and look stupid as it lowers it's humongous foot to squash them, but instead falls on it's arse thanks to an explosive arrow hitting it's ankle.

Their saviour is Beta, a female Autobot who lets them follow her, doing so simply because they bear the same symbol of shame (Autobot insignia!) she and her warriors do, who need all the help they can get in their war against the Quintessons, their brutal masters. As Beta shows them the other warriors they have (warriors being a fairly loose term when it comes to technicians and servants), Rewind deducts that yes, they are in ancient Cybertron, and the Quintessons have removed A3, the leader of this rebel group in an attempt to prevent the uprising from ever happening and change the future! How devious.

Back in the present, Silverbolt notices that the time window is leaking energy out into space, while Pipes isn't having much luck getting Perceptor back into good shape. The Quintesson supervisor, meanwhile, watches the time window's leakage with fear, explaining that it will go to Cybertron, Earth and infinity if it is not stopped, causing everything to happen throughout the universe!

For example, Wheelie's unfair win against Bumblebee, Jazz and Springer in a race on Cybertron will repeat twice.
 

Certain events will be reversed, such as this flood fixing itself. I think. It's not a good example.
 

Past and present will collide! And this is demonstrated by Marissa Faireborn doing a little sharp shooting practise, only to turn into an infant.

"Ultimately, as every natural law breaks down, the universe will cease to exist!"

The Quintesson states the only solution is to destroy the time window, while Rodimus gets chatting with this new guy who believes him to be a spy for the Quintessons, but before the Autobot leader can defend himself, bombs are dropped from the Quintesson warships, followed by an army of Sharkticons who get scrapping with the Autobots. The moustached guy gets caught in an explosion...

... and is somehow propelled into space. Superion rescues the dude but is promptly cornered against an asteroid by Quintesson warships, making the big lug feel like a bit of a doofus. His handheld partner tells him not to give up or else he will be removed from existence, and briefly turns into Alpha Trion but stating his name as A3!

Superion is then caught in the time rings, and then appears where he was before, fending off Quintesson ships, putting him in two places at once! Realising that things as a whole are going pear-shaped, the Quintessons retreat, giving Pipes the opportunity to continue repairing Perceptor.

Back in the past, the group go with Beta to the war zone and encounter a hoard of Guardians, and just when they think planning ahead would be a swell idea, Ramhorn charges on ahead and everyone else follows suit. Mob mentality is a terrible thing.

In the present again, the Quintesson supervisor appears in the stars somehow to alert the Autobots that they must put aside their differences and destroy the time window. Completely ignoring the "put aside our differences" part, they start bickering and think it's a trick, what with some of their buddies still being in the other side. And those guys in the past look like they're faring pretty well against the Guardians...

Until a Quintesson shows up, says he was watching the whole thing and was dissatisfied with it, telling the Autobots to put down their weapons or else the Guardians will vaporise them, which really is pretty stupid if they listened long enough for those to completely surround them and put them at a disadvantage. Sometimes just shooting the villain and ignoring proper justice is the best way to deal with matters, you know.

Rodimus is then led through the procedure of closing the window by the Quintesson, but stops at the final step, claiming they have to rescue their buddies first. A3 steps up to the task, even though he believed Rodimus and the gang to be spies, and leaps through the window. This simple act causes the Quintesson in the sky to scream "no!" and vanish, what with his devious plan being foiled and all, but why he vanishes is beyond me.

A3 lands in the past and embraces Beta before removing his Autobot insignia, turning it around and spraying a beam of light at the Guardians, causing them to shield their faces pathetically and fall down dead. Telling the stranded Autobots that their friends need them, they obey and make an exit through the time window, allowing Rodimus to fully close it. Being a cartoon, "close it" means "it explodes".

Perceptor is finally reawakened, who claims they must close the time window, but that's old news by now. Rewind then realises something; A3, the leader of those rebel Autobots, is an abbreviation of Alpha Trion. "That was the guy who created Optimus Prime? He was the father of all of us? You gotta be kidding."

If you haven't seen any of the other history-providing episodes of Transformers in season 2, then this one won't make a whole lot of sense. Which is unfortunate as I'm one of those people.

The former Wikipedia article of this episode says "A-3 arrives just as the deadline was up and uses his coda remote device to deactivate the Dark Guardians" about the part where A3 flips his insignia around. Either that is bullshit or the episode could've done with an extra two minutes to explain that convenient tide-turning. Or I could've just missed something. Wouldn't be the first time.

Just who are these guys meant to be?

They're the size of humans, but they sure aren't coloured like anything recognisable, and those sure aren't exosuits.