"Yesteryear"
We met Spock's parents in the TOS episode "Journey to Babel," and visited Vulcan in "Amok Time," but this episode featured the most extensive visit to the planet itself. Another great thing about his episode is the time-traveling peek at Spock's youth. At the top of the episode, we revisit the Guardian of Forever (from "The City on the Edge of Forever"), as Starfleet now uses the portal to study ancient histories across the galaxy. When Kirk and Spock return from an observation mission, no one recognizes him, and there's a new First Officer, an Andorian named Thelen. Thus Spock has to travel back in time via the Guardian and set the past straight. Treats for fans in this episode include the voice of Mark Lenard as Sarek and we get to see Spock's pet Sehlat referred to in "Journey to Babel." Also, the prejudice and the cruelty of children is shown as other Vulcan children taunt the young Spock for his half-human heritage, a theme that resonates for young and older audiences alike.

"More Tribbles, More Troubles"
Star Trek's classic humorous tribble episode is revisited in this episode, written by "The Trouble with Tribbles" author David Gerrold (who also voices the character of Korax). Stanley Adams, who played shady entrepreneur Cyrano Jones, reprises his role, as the Enterprise and crew rescue him from attacking Klingons while escorting two shipments of grain to Sherman's Planet. Jones now has "safe" tribbles, genetically manipulated not to breed, as well as a Glommer, a "tribble predator." It turns out that Jones had stolen the Glommer from the Klingons, who needed the creature to save one of their planets from becoming overrun with tribbles. The concept of ecological devastation from a non-indigenous species (even one as seemingly harmless as tribbles) reflects the series' use of complex themes despite the Saturday morning "kids" audience.

"The Infinite Vulcan"
While he wasn't able to hire on Walter Koenig to play Chekov, Roddenberry did hire him to pen this episode which delves into some pretty heady territory for a "cartoon." The Enterprise arrives at a planet to find a species of intelligent plant life that had been almost destroyed by disease brought by humans when they first visited decades earlier (a plot point sadly reminiscent of similar diseases which decimated Native Americans in the Americas). Kirk and his landing party also discover a fifth-generation clone of the original surviving human, Dr. Stavros Keniculus, who seeks to bring peace to the galaxy by creating a super-clone of Spock. This episode is a good example of the freedom that the Animated Adventures had that a live show would have trouble paying for, such as giant clones, intelligent plants both large and small, and flying creatures that kidnap Spock.

"Mudd's Passion"
The return of Harcourt Fenton Mudd (voiced by Roger C. Carmel, who played him on TOS) sets into action a series of events that force the Enterprise crew into some rather, er, compromising situations. Mudd is discovered selling a fake love potion to lonely miners on the planet Motherlode, but he manages to con Nurse Chapel into freeing him in exchange for actual love crystals to use on Spock. When the crystals accidentally end up in the ship's ventilating system, the entire crew gets affected with humorous results. Again, it's a treat to see TOS characters return, voiced by the original actors.

"The Terratin Incident"
One of the distinct advantages the Animated Adventures had was the low-to-non-existent special effects budget, allowing for non-humanoid crew members like the red alien Lt. Arex or the feline Lt. M'Ress. In this episode, events lead to the entire crew becoming victims of a strange effect which shrinks them, rendering them smaller and smaller. Rather than just settle on saying "they're shrinking," writer Paul Schneider explains that the effect is the result of the space between molecules constricting, an added scientific nugget that gives viewers (especially younger viewers who know nothing about DNA, atoms or sub-atomics) something more to chew on than some miraculous "magic." Also, this episode is fun just to watch the familiar crew so small that they have to stand on each others' shoulders to make the automatic doors recognize they're even there.

"Slaver Weapon"
This episode was written by legendary science fiction author Larry Niven (the Ringworld series) who delivers a unique take on some familiar themes in an unorthodox manner. To start with, the entire episode takes place away from the Enterprise, with Spock, Uhura and Sulu in a shuttlecraft en route to Starbase 25. They have a stasis box from the ancient "Slavers," a long-dead race that once ruled the galaxy. Slaver stasis boxes often contain artifacts and technology sometimes beyond anything "modern," and the boxes themselves can sense other boxes, which leads the trio of Starfleet officers into a trap set by the cat-like Kzinti. In an interesting twist, the Kzinti are portrayed as a warlike race with a prejudice against females and vegetarian beings. These meat-eaters have no time for Spock or Uhura, a mistake that Sulu takes advantage of. The Kzinti find a Slaver weapon (hence the episode's title), a multi-purpose device which ultimately costs the Kzinti their lives, proving the dangers in pursuing ultimate power.

"The Jihad"
Long before the term "Jihad" grimly made its way into the mainstream American vernacular, author Stephen Kandel used the term for this episode, an adventure-quest in which Kirk, Spock and several other beings must find and return a stolen religious artifact to avert a galactic holy war. The stakes in this episode are especially high for a Saturday morning cartoon — the implication of a galactic war in which billions could die is sobering stuff. The team that is selected and assembled for the task each have specific characteristics and qualifications (Kirk for his leadership, Spock for his scientific prowess, etc.) which underlines a theme of everyone serving a purpose. Slightly older audiences will find the huntress Lara's advances on Kirk eyebrow-raising, to say the least.

"The Pirates of Orion"
In this episode, Spock is stricken with a disease that is mostly harmless to humans, but deadly to Vulcans. A shipment of a drug which will save him is hijacked by Orions. Now, in terms of Star Trek continuity, these "Orions," while spelled the same as the green-skinned Orions (such as Vina in her slave-girl guise from "The Cage") must be a different species. They're not green-skinned, and Kirk pronounces them as "Oh-ree-uns" instead of "Oh-rih-ans." That must be it. In any case, this episode highlights the close bond shared between the three leads, with Kirk and McCoy doing whatever it takes to cure Spock. McCoy even talks about how, despite how exasperated he gets with Spock, that "walking encyclopedia," he wouldn't want to lose him. When caught, the Orions attempt to destroy themselves to avoid capture and possible repercussions to their homeworld's neutrality. While unsuccessful, the attempt is another example of the mature and complex themes that Roddenberry never shied away from when making the show.

"How Sharper Than a Serpent's Tooth"
The Enterprise and crew follow a mysterious probe's waste trail until they find a larger ship, which imprisons the Enterprise in a force bubble and steals away Kirk, McCoy, Scotty and a Native American crew member, Ensign Dawson Walking Bear. Walking Bear, a Comanche who has studied many of Earth's early cultures, recognizes the ship's lone commander as Kulkukan, a winged dragon who had visited Earth centuries before and was seen as a god by the Aztecs and Mayans. Kulkukan still sees humans as children in need of guidance, but Kirk and his crew demonstrate mankind's maturity and peaceful nature. This episode is notable not only for its Shakespearean title (the quote comes from "King Lear") but for its depiction of early Earth cultures. In a way, it both honors and debunks early deities, first by depicting them, and then explaining them as originating as alien visitations.