"Assignment: Earth" is the only TOS episode staged entirely in another time, literally set aside from all the others. As such it doesn't fit well in the Trek-verse, revealing mankind as not smart or self-reliant enough to progress without help (though at times this certainly resembles some of Gene's other ideas). The story supposedly evolved from an unsold non-Trek pilot written by Roddenberry trying to spawn another series were TOS not picked up for its third season. Sadly this forced and clumsy interface hobbles both premises, in that it explicitly depends on the inactivity of the Enterprise crew. Time travel episodes are bad enough, blithely and (usually) nonsensically tramping over one of the toughest challenges in physics, yet aggravating that situation is placing the best ship and crew in Starfleet more or less on librarian patrol!

Anyway not only has the idea not aged well, frankly it was obsolete from the start. (Roberta's purse is still cool though.) In the 1968 of Gary Seven, Earth has a sky full of H-bombs on suborbital platforms, a situation dire of course yet never actualized then or now. In his role as super interplanetary secret agent the late Robert Lansing does an acceptable job, armed with his bliss-hitting servo and accompanied by the strange feline shapeshifter Isis. And the biggest (somewhat silent) regret is that acclaimed actress Teri Garr went into such painful meltdown regarding the experience that discussing the subject remains verboten.

It's certainly not all bad and quite occasionally enjoyable, like the decent view of Earth seen from space, or even the annoying but sassy Beta 5 computer. The talk-to typewriter ("Stop it! Stop it!") can still bring a smile after many viewings. The crew is only seen briefly then neglected (and though he appears it's distracting to see Paul Baxley out of a Starfleet uniform!) Only Scotty gets real screen time bouncing weather satellites and hopefully getting good callback on the "hidden" planet's transporter signal. (Hmm, maybe the interception of Seven was really why they were sent back!)

Spock's observation regarding "human intuition" became an enduring tone of the show's philosophy, but any episode with Kirk intentionally held helpless cannot by definition be a great episode. It's unlikely though that the "Gary and Roberta" show would have ever gone anywhere. Without limits to the power of nerve-pinch-proof Seven (and servo and Beta-5 computer!) it would have grown too boring, too formulaic. Their adventures did continue in a few enjoyable novels, but thankfully this is one assignment that went no farther.