I'll start off small, but keep reading.
Random Trainers didn't have names until Gen II. In practically every game since Gen II, there has been a random Trainer named Ikue that uses Pikachu as a referral to Ikue Ohtani voicing Pikachu. This isn't totally apparent because it wasn't always kept as Ikue in other versions. For an example, in GS, Picnic Girl Ikue was localized as Picnicker Brooke.
Where this starts to get obscure though is that the vast majority of Japanese names are references to real people or plays on words. For example, there's Bird Keeper Tsubasa (翼 tsubasa means wing(s)) and School Kid Manabu (学ぶ manabu means to study/learn). There are numerous NPCs named after all sorts of people in the Pokémon franchise, like Guitarist Jun'ichi (from Jun'ichi Masuda), to Poké Fan Megumi (from Megumi Hayashibara who plays Jessie) to Cool Trainer Ken (from Ken Sugimori). Guitarist Masuda from Crystal's Battle Tower only exists in international versions of the game, he wasn't the original reference. But what's even crazier is that 4Kids would often use the localized names when their Japanese equivalents appeared in the anime. For example, Guitarist Jun'ichi and Shorts Boy Kenta were renamed to Guitarist Vincent and Youngster Jimmy in the localized GS. These same localized names would be used for the characters Jun'ichi and Kenta (Vincent and Jimmy) in The Legend of Thunder dub years later, and there are more examples you can find throughout the Johto anime.
There are two unseen characters only mentioned in phone calls as wrong numbers, and those are Atsuko (Audrey and some new name in Crystal) and Tsunekazu (Kaz) from Atsuko Nishida and Tsunekazu Ishihara. Also, many names had set localizations since many names were reused from game to game. Gorou is almost always localized as Joey for example, but it can be inconsistent.
