Original air date: January 26, 1967
Establishing shot: Stock Footage of an air force base..... from the 1960s. The RADAR detects a signal from just over Omaha, Nebraska. The officers discuss the unusual UFO that seems to have come from nowhere. Just when we're thinking some old war movie is being played by mistake, we hear the Theme Tune and see the Enterprise gliding through a blue sky and clouds.
According to the Captain's Log, the Enterprise encountered a black star of high gravitational attraction that forced them to use all their warp power to escape the pull, which propelled them plunging through space...and time itself! There's no signal from Starfleet and the Enterprise is being tailed by a relatively primitive craft. It is, however, armed with some nuclear warheads that could do more damage than they're able to repair in this time period, so they break out the Tractor Beam. It turns out to be more than the jet can handle, so the pilot is beamed aboard. He introduces himself as Captain John Christopher, 4857932. Kirk assures him he is not a prisoner and takes him to the bridge.
So, the Enterprise is trapped 200 years in the past with a "guest" who doesn't want to stay, but they can't let go. The engines are shot. They have no way of contacting Starfleet. There's massive injuries from that star that slapped the ship around like a pinball. And Kirk's computer is flirting with him.
Tomorrow is Yestertropes:
- 20 Minutes into the Future: The crew goes back in time to the late sixties—where they pick up a radio broadcast talking about a manned moon launch coming up, establishing it as being a bit later in the sixties than when the episode was made.
- The Omaha installation was never named, possibly to avert this trope. In the late '60s, many military bases were being closed and renamed and units moved. However, it was called Offutt Air Force Base then and as of 2017.
- Accidental Time Travel: Sling-shot back to the 1960s trying to escape a black star. Interestingly this method proves replicable in later episodes (and movies).
- Artistic License – Military: F-104 Starfighters, such as those shown in the beginning Stock Footage and piloted by Capt. Christopher, were never stationed near Omaha. If they had needed to scramble fighters, they would have used F-102s from Richards-Gebaur Air Force Base (Grandview AFB from 1952 to 1957) Missouri.
- Kirk also introduces Spock to Christopher as "lieutenant commander," even though Spock has been wearing full commander insignia for pretty much the whole danged show by now.
- There was never a 498th Airbase Group. There was a 498th Fighter Interceptor Squadron stationed at Paine Field in Washington until 1966, when it moved to Hamilton AFB in California. The 498th FIS flew F-106A Delta Darts.
- The security forces who capture Kirk while Sulu is in the dark room have haircuts that are clearly non-regulation.
- Captain Obvious: Spock seems to believe that's what Bones is being when he describes the danger Kirk is in.
- Cassandra Truth: When asked how he got into the security area, an exasperated Kirk tells him, "I popped in out of thin air." And, that's exactly how the transporter works.
- Changed My Jumper: Captain Kirk beams down to a 1960s U.S. Air Force base while wearing his Star Fleet uniform. This is probably attributable to Early-Installment Weirdness, as the producers at the time were likely unaware that the Enterprise has fabricators which would later produce a 1940s Nazi SS uniform, so a 1960s US Air Force uniform should have been no problem. note
- Deadpan Snarker: McCoy suggests that Spock admitting to being wrong is a historical moment.
- Kirk's snarks under interrogation are some of the funniest moments in the show.
- Don't Touch It, You Idiot!: In a Funny Background Event, Uhura has to tell Christopher that he had better keep his hands away from the buttons of the Enterprise bridge's consoles.
- Early-Installment Weirdness: Kirk explains to Christopher that the Enterprise operates under the auspices of the United Earth Space Probe Agency (UESPA), rather than Starfleet Command, which wouldn't be introduced until the next episode. The popular Fanon explanation is that Kirk was still trying to hide as much about the future as he could...which really doesn't explain that much. Besides, Kirk also mentioned UESPA in "Charlie X". Starfleet Command is instead called "Starfleet Control."
- Fish out of Temporal Water: Christopher would be one if the Enterprise took him back to the future, and the Enterprise and her entire crew are for the duration of this episode.
- Framing Device: The 1975 Star Fleet Technical Manual by Franz Joseph credits the events of this episode as the source of all the manual's content. Somehow, USAF computers were able to download a great deal of information from the Enterprise's library computer detailing the Federation, starships, Starfleet, and a slew of other data. It was apparently the result of a standard procedure info-dump that starship computers are programmed to perform whenever in range of a compatible, friendly receiver. The Air Force must have made the cut.
- Get Back to the Future: While breaking away from a black hole, the Enterprise is flung back in time to the late 1960s. They must find a way to reverse the effect to return to their own time.
- He Knows Too Much: The reason given for keeping Christopher on board.
- Little Green Men: Christopher comments that he has never believed in "little green men"... just in time to encounter a certain first officer.Spock: Neither have I.
- While being questioned, Kirk claims to be a little green man from Alpha Centauri.
- Matriarchy: The planet Cygnus XIV, where the Enterprise was put in for maintenance and which gave the ship's computer its flirtatious female personality, is mentioned as being female-dominated.
- Mistaken for Aliens: Christopher thinks the crew aboard the Enterprise are aliens. Well, not all of them are.
- Mistaken for Spies: The officers of the USAF assume Kirk must be a spy, trying to steal privileged information.
- Mundanization: Space age jets are like balsa gliders compared to the Enterprise. Sulu and Kirk need to steal a pre-digital era film reel to protect the time line. Kirk marvels at the sight of an old relic known as a "cork board".
- Morton's Fork: Spock does some research and learns that Christopher must be returned to his timeline in order to father Shaun Christopher, who will be on a probe mission to Saturn, or else history will be disastrously changed. But if they return him, he will be duty-bound to report everything he's learned about the future, and history will be disastrously changed.
- Nice Job Breaking It, Hero: Kirk saves Christopher by having him beamed aboard. Now he has the problem of returning him to earth. This is probably why Starfleet has policies on time travel now. At least half of Starfleet rules must be the direct result of something Kirk did.
- He did apparently have the "biggest file on record" with the Temporal Investigations department.
- Now Do It Again, Backwards: How the Enterprise returns to its own time.
- Oh, Crap!: Kirk gets an "Oh, crap!" look on his face when Air Force officers catch him in the act of stealing photographs. And an even bigger one as they play with his phaser.
- Plot Hole: Selective memory erasure techniques apparently didn't exist in the 23rd century. That would have instantly solved the dilemma of returning Captain Christopher home with knowledge of the future. Spock has also shown in future episodes that he has the ability to use a mind meld to erase an unwanted memory.
- Reckless Gun Usage: Justified; the Air Police who capture Kirk don't know one piece of his gear from another, and a hand phaser looks more like an electric shaver than any 20th-century weapon. Still, they play with it casually and toss it around. If you watch their fingers, they come within a literal hairsbreadth of shooting him or each other more than once.
- Sexophone: One plays when one of the miniskirted Bridge Bunnies walks past Christopher, who's dumbfounded to find a woman on board a military vessel.
- Shown Their Work: The Enterprise travels back in time to the late 1960s. It's mentioned that three astronauts are taking part in a manned moon shot on Wednesday. Two years after the episode aired, Apollo 11 blasted off on July 16, 1969 (a Wednesday) carrying three astronauts (Neil Armstrong, Buzz Aldrin, and Michael Collins). Given that the Apollo program was already getting started around the time of this episode, however, it was already known that there would be three astronauts per spacecraft, and odds were good that at least one of the craft bound for the moon would launch on a Wednesday.
- Stock Footage: Footage of the Earth (going closer and further, inside the atmosphere) on the Enterprise viewscreen is reused from "Miri".
- Tap Onthe Head: Sulu knocks out a U.S. Air Force officer by hitting him in the neck with a karate chop.
- Time-Travelers Are Spies: When the Enterprise accidentally travels back in time to Earth in the late 1960s, Captain Kirk is considered a spy when he's caught infiltrating a U.S. Air Force base. (When an interrogator threatens to lock him up for two hundred years, Kirk ruefully acknowledges, "That ought to be just about right.")
- Time Travel Episode: Star Trek's first real attempt at this.
- Timey-Wimey Ball: Here's the solution to their little problem: Mr. Spock says that the best possible course of advantage is to use a slingshot effect like the one they used to arrive in the first place. Theoretically, the whiplash from the sun's gravity would send them into another time warp. At this point, Christopher asks what they will be doing about him and the guard. Spock states that for a moment, they will go into the relative past, and transport both the captain and the guard to points before they were beamed up, so that the events will never have occurred. (It's never expressly stated if they remember the experience or not, but the scenes we see suggest they don't.) Don't think about it too much.
- Tractor Beam: The Enterprise uses one on Christopher's plane to prevent it firing its missiles. It's powerful enough to crush the aircraft.
- You Have GOT to Be Kidding Me!: Kirk just gives an incredulous "What?" when told they've traveled in time.
- You Wouldn't Believe Me If I Told You: Kirk tells his interrogators this when they demand to know how he got in their dark room. Nor would they if he had.