Common Sense Note
Parents need to know that, compared to today's visually stunning special effects, Star Trek: The Original Series was very low-budget in both props and special effects and may consequently seem silly to modern kids. But beyond that, the series was a metaphor for the upheaval of the 1960s. Behind the storylines of space travel and aliens are important social commentaries on racism, sexism, politics, and the fear that machines might one day rule the world. Taken at face value, though, most of the adventures are pretty innocent and are fine for young tweens and up.
Women wear skimpy, skin-tight outfits (with mini-skirts and go-go boots). Some alien races portray women as subservient, while others have women in power. Crew members often flirt -- most notably, Capt. Kirk, who falls in love quite often. Some kissing (including a groundbreaking interracial kiss between Kirk and Uhura).
Most episodes include some fighting, be it characters physically wrestling each other or using "phasers" (their weapons) or photon torpedoes. But blood is never shown. Mind control is a frequent plotpoint.
Mild overall. "Dammit, Jim!" -- uttered by Bones -- occurs in many episodes.
The show's overall message is to respect one another's differences. Storylines often revolve around alien races with different social norms than humans (sexism, racism, politics), but the Enterprise crew isn't supposed to interfere.
Lots of Star Trek products out there, but nothing in the show itself.
Drugs / Tobacco /
Some drinking by adults in social settings. Scotty is often involved in drinking contests with other humans and aliens.