Re: Never seen TOS scenes...
The mirror universe ISS Enterprise enters Federation space through a trans-dimensional portal. With the Terran Empire in disarray and rebellion (due to goateed Spock), Kirk, the ISS Enterprise, and one loyal ship head to the "mirror universe's Federation" for plunder and power.
The USS Enterprise, patrolling the Romulan Neutral Zone, is sent by Starfleet at high warp to investigate a huge spacial anamoly that has suddenly appeared 15 light years away.
Caught by surprise as the Terran Empire ships exited the portal, this universe's Kirk and Spock realize that they cannot defeat the ISS Enterprise and ISS Devastation.
Instead, Kirk and Spock convince the ISS ships that Romulan worlds are ripe for the picking. They even have the ISS Enterprise scan the region. There are "no" ships protecting the Romulan worlds along the neutral zone.
Additionally, by this time, 6 Starfleet vessels are approaching. The ISS Enterprise and Devastation, looking for easy prey, cross the neutral zone and head towards the apparently undefend Romulan worlds....
Scotty asks the Captain, "don' they know the Romulans have cloaked ships?"
Spock answers for the Captian: "When the captain was in the mirror universe last year, he happened upon a history book which noted that the Terrans defeated and conquered the Romulans almost 100 years ago, long before they had cloaked ships."
Scotty, "Aye, I almost feel sorry for them, almost..."
The Romulans just assumed that this was Federation retaliation for their recent border incursions...
(Edited: Added phaser and photon fire and fleshed out the story and correct way too many mistakes and I'm sure I missed a couple along the way)