Opening shot: a lovely view of Spock's back. Just as he's giving his survey analysis of the uninhabited iron-silican planet the Enterprise is orbiting, everything rocks violently and we get a double exposure image of a nebula. Yeah, get used to this effect, you'll be seeing it a lot. Make a Drinking Game of it if you wanna get hammered. Once everything stops shaking, they realize that the planet is no longer quite so uninhabited.
Kirk, Spock and more Red Shirts than you can shake a stick at beam down to Kirk's Rock to find a crashed Flying Saucer. They also meet Lazarus, who rants about death and destruction as he takes a pratfall off the rock he's standing on.
Lazarus rants about a "monster" that destroyed his civilization that must be destroyed. According to Spock, there is no other life form on this planet. And... overlay of the nebula again.
Lazarus, meanwhile, has enormous mood swings and a scrape on the forehead that seems to disappear and reappear. And that beard goes from thin to thick after every ad break.
- Absentee Actor: Scotty and Sulu are absent. For unknown reasons they were substituted in the roles of engineer and helmsman by Charlene Masters and Leslie, respectively.
- Alternate Self: Lazarus and Lazarus.
- Ambiguously Human: Lazarus and his alternate universe counterpart: were they human, or Human Alien? The episode itself seemed confused on this point.
- And I Must Scream: How both versions of Lazarus end up.
- Antimatter: There are two versions of Lazarus, one made of matter from our universe and one made of antimatter from a parallel universe. If they ever get together in either universe, the results will be disastrous.
- Artistic License Chemistry: Spock declares the planet they are orbiting has a "oxygen-hydrogen atmosphere". This is extremely unlikely, as oxygen and hydrogen are highly reactive and react rather violently with each other, producing water. Specifically, this is the strongest chemical reaction per weight unit we know about, and we use it in rockets like the Space Shuttle to get satellites and other equipment into space. Very likely Spock wanted to say "oxygen-nitrogen" instead, describing an atmosphere like the one we currently enjoy on earth.
- Artistic License Physics: Nearly everything anyone says about antimatter. For one thing, matter-antimatter annihilation happens on a much smaller scale than people and antipeople, so antiLazarus should have exploded the first time he encountered any matter, not just the lump of it that happened to be shaped like him. Also, while the resulting explosion would have been quite dramatic in human terms, it would hardly affect anything beyond the planet, let alone threaten the entire universe.
- Ax-Crazy: Lazarus demonstrates himself to be this with the following outburst with regards to Anti-Lazarus:Lazarus: He'll kill us all if we don't kill him first! KILL! KILL! KILL! KILL! KILL!
- Big "NO!": Lazarus lets out one of these when Kirk vanishes into an antimatter universe.
- Early Installment Weirdness: The crystals that power the Enterprise are called "dilithium crystals." In earlier episodes (such as "Mudd's Women") they were called "lithium crystals." Here they appear as blocks of amber rather than actual crystals.
- Everything Sensor: The failure of the sensors is sufficient proof that a parallel universe is involved:Spock: Our ship's instruments are specifically designed to locate and identify any object in our universe, be it energy or matter.
- Go Mad from the Revelation: Matter!Lazarus goes stark raving mad upon learning of the existence of his Anti-Matter double and becomes hellbent on destroying him, even if it means the destruction of both universes.
- Hell Is War: Matter and Anti-Matter versions of the same man are locked in combat forever in the corridor separating their universes.
- Heroic Sacrifice: Anti-Matter!Lazarus views his eternal struggle with his double as this.
- The Klutz: Lazarus makes Chevy Chase look graceful! He falls a total of three times and several times looks like he's about to fall if weren't for that handy wall.
- Large Ham: Lazarus makes Kirk look subtle. It doesn't help that the actor (Robert Brown, later from Here Come the Brides) was a last-minute hire, owning to the original actor, John Drew Barrymore, failing to show up for work the day filming was to begin.
- Meaningful Name: Lazarus was a man who was resurrected. The two Lazaruses (Lazari?) are forever in a cycle of non-death.
- Never the Selves Shall Meet: Two identical men named Lazarus. One is from our universe and insane. The other is from an anti-matter universe. Apparently, if both meet in the same universe, it destroys both of them.
- Omnicidal Maniac: Matter!Lazarus is so far around the bend that he doesn't care if he and both universes are destroyed, so long as his double goes with him.
- Sealed Evil in a Can: If Lazarus and his insane counterpart from the antimatter dimension were ever to meet in the same universe, that universe would be destroyed. Both of them are sent into an intermediate dimension so that this can never happen, and where the two of them will be locked in combat for all eternity.
- See You in Hell: "Come! Come! It'll do you no good! I'll chase you to the very fires of HELL!!!!"
- Understatement: Kirk remarks that Lt. Masters has a knack for this when she says that the Enterprise will be at risk without the power of the dilithium crystals.
- Vehicular Sabotage: The Enterprise qualifies as a vehicle, right? In this case, Lazarus swaps a few banana plugs in a control panel to cause an electrical fire that will distract the engineering crew long enough for him to steal the dilithium crystals.