I assume most people here are aware of the feature in Crystal where the happiness of a Pokemon that is trained at the place where it was first met or hatched is doubled. What surprised me, however, is that Pokefan Trevor says "If only there were an easy way to identify where I got my Pokemon" after alluding to the mechanic. It struck me that while Crystal was the first game to keep track of the location, level, and even time of day that the Pokemon was first met, the met location wasn't displayed on the summary screen since Crystal uses the same summary screen as Gold and Silver. You'd have to go to the Pokeseer (the old lady in the north of Cianwood) to find out that information. However, the met location was included in the summary screen starting from RS onwards and that's probably what Pokefan Trevor meant by "easy way to identify where I got my Pokemon." It's a nod to the fact that Gen III was in development at the same time as Crystal, which should've been obvious since that had been the case with all generations and Kecleon showed up in the middle of the Johto anime, but I didn't know there were hints to this fact in the game itself.