This is the third episode in which a Pokémon from a new generation appears. The first two were Pokemon Kimi ni Kimeta! (1997) and its ensuing flashback in Tai ketsu! Pokemon senta! (1997), respectively; in both episodes, Ho-Oh appeared. This is also the first episode where a main character obtains a Pokémon from the following generation.
This is the first episode to show a Pokémon hatching from an Egg.
This episode marks the first of the many times in which Pikachu saves Togepi, though it is also the only one of those times in which these efforts are noticed by anyone else.
In the dub, Professor Oak states that the Pokédex upgrade includes a new voice. This was done to provide an in-continuity explanation for how Eric Stuart takes over as the voice of the Pokédex from this episode onward.
Even though it is implied a few times in the episode that Brock knew the concepts of breeding and/or raising Pokémon Eggs, he doesn't seem to know about imprinting until after the Pokédex reveals why Togepi wanted to go to Misty.