The Pokémon that was unidentified at the end is named Ho-Oh, making this the first appearance of that Pokémon.
This is the only episode where Ash's Pokédex talks while it's closed.
Ash is based on Red, a character from the Pokémon Adventures Manga and main character of the Red, Green, Blue, and Yellow video games.
Ash reveals that Squirtle was his first choice and Charmander his last.
Gengar and Nidorino are the first two Pokémon shown in the series. However, the first Pokémon to be physically seen on the show was Dodrio, where it was shown crowing like a rooster in Pallet Town to bring the morning. The Pokémon that had appeared beforehand were either on TV, in dreams, or not real.