One wonders if they could've done a show like Cause and Effect. You just know the Enterprise blowing up in the teaser would've shocked the hell out of a 60's audience. I wonder what their idea of a Starfleet ship a century older than the Constitution class would look like. (Notice I was careful not to say a 22nd Century ship, since they never did peg down the century on the original series. I believe as late as the writer's bible for the Star Trek II series, they were being intentionally vague). Would've been neat if they could've gotten a well-known actor from some popular show on at the time to cameo as the captain of the other ship, as Kelsey Grammer did.
Final scene of the episode...
SPOCK: We have successfully avoided collision with the other vessel, Captain.
KIRK: Well done. Identification on the other ship?
SPOCK: It appears to be a Federation vessel, Captain, but that design has not been used in some time. I shall attempt to gather further data with the sensors.... Fascinating! The vessel reads as an old-type scout vessel of the Sherwood class. Judging from the vessel's markings, it appears to be the U.S.S. Minnow - listed in Starfleet records as missing in action for 78 years, 4 months, and 2 days.
KIRK: Uhura, open hailing frequencies!
UHURA: Hailing frequencies open, sir.
KIRK: This is Captain James T. Kirk of the Federation Starship Enterprise - please identify yourselves!
The screen lights up and we see an image of the other ship's bridge with her familiar-looking captain and first officer in view...
CAPTAIN: Hello, Enterprise - This is Captain Jonas Grumby of the U.S.S. Minnow, and this is my first officer, Commander William Gilligan. We have just been through an extremely violent temporal storm of some kind - if not for the courage of our fearless crew, we would surely have been lost. We have a hull breach and need immediate assistance. Do you read, Enterprise?