The Enterprise is in pursuit of a small vessel. The vessel is destroyed but Scotty manages to beam off the "crew," which consists of "entrepreneur" Harry Mudd and three captivatingly beautiful women. It turns out the three women are not so much crew as cargo; they were going to be wives for settlers. But the Enterprise sustained damage during their pursuit of Mudd's ship, forcing Kirk to head for a mining colony for more lithium crystals.
- Early Installment Weirdness: Another episode with references to "lithium," which would later be called "dilithium," and Spock being referred to as "Vulcanian." Uhura is seen in the gold command uniform.
- Emergency Refuelling: Rescuing Harry Mudd's ship destroys three of the Enterprise's four dilithium crystals and damages the fourth, so they have to travel to a lithium mining operation on Rigel 12 to get more.
- Feminine Women Can Cook: Even in the future women are expected to be good cooks!
- Gaussian Girl: Part of the supposed "self-confidence" which is all women need to be beautiful.
- Hidden Depths:
- Childress apparently just wanted a woman to hang around and be pretty, but starts to look at Eve in a new light as she reveals herself to be cleverer than he expected.
- Mudd at first appears to be some kind of pimp or even slave trader when he insists on calling the women "cargo", but he's basically the only one who consistently treats them with any kind of respect.
- Human Outside, Alien Inside: It's mentioned in passing that Spock's heart is over to one side and further down than a human's heart would be.
- Lie Detector: During the hearing, the computer constantly replies "Incorrect!" when Mudd is lying. Mudd mutters about the "blasted tin pot" when it pulls up his criminal record.
- Magic Feather: Three women are supposedly given a "Venus drug" which made them irresistibly beautiful, but it revealed at the end that they didn't need the drug to make themselves beautiful - it was self-confidence all along. The on-screen moral being: apparently self-confidence can give you an actual makeover — complete with makeup and a new hairdo!
- Mail-Order Bride: The three women.
- Male Gaze
- Ms. Fanservice: Eve, Magda, and Ruth.
- My Sensors Indicate You Want to Tap That: During the hearing into Mudd's reckless piloting, Kirk initiates a computer scan of all present intended to discover if Mudd or his passengers are showing physiological reactions indicative of dishonesty. The computer reports negative, then volunteers that most of the male crew present are showing physiological reactions indicative of attraction to the women.
- However, McCoy's sickbay instruments go haywire whenever one of the women walk past.
- Space Western: The episode uses several well-worn tropes of the genre. Mudd is essentially a hustler selling women to settlers out on the frontier, although the implications of this are not explored in any detail.
- Sherlock Scan: Mudd apparently can do this, correctly noting that Spock is part Vulcan despite him looking like pretty much every other full-blooded Vulcan. However, this could also be yet another case of Early Installment Weirdness - both of the previous episodes to be filmed ("Where No Man Has Gone Before" and "The Corbomite Maneuver") are explicit in establishing Spock as half-Vulcan; the writers may have originally intended for full-blooded Vulcans to look considerably less human than Spock does.
- She's Got Legs: Magda.