Pippi to Tsuki no Ishi

The first, in what would be hundreds of episodes in the quintessential Pokemon format - Ash + two companions and Pokemon visit a place along their journey, typically fighting Team Rocket along the way.

We still stay close to the first games for this outing, leaving Pewter city and heading to Mt. Moon, where the gang meet a group of Clefairy and an eccentric researcher by the name of Seymour the Scientist. This one is heavy on the slapstick and laughs, mostly at the expense of Team Rocket as they attempt to make off with the mysterious Moon Stone ensconced somewhere in the mountain.

Watching with the power of hindsight, it's interesting to see some other early elements of characters that haven't yet settled into their final versions.

Specifically, Meowth is still eluded to have some form of leadership role within the Team Rocket trio, as well as having some aptitude for battle on his own, and even though he's quickly dispatched in Pokemon battles, he does choose violence more readily in early outings.

In this early stage, Ash and Pikachu's bond is also not as deep as it eventually becomes and this episode features a fun example of Ash having to interpret what Pikachu is trying to say through pantomime and charades - a method which is eventually retired as the understanding between them grows.

This serves as a great template example of any of the shows general adventure based episodes.