I have a few

One of them is when I got my first shiny Pokemon, it was a shiny luvdisc in Emerald and the only reason I wanted it was because it sparkled. I didn't even know why. But it was sparkly so I wanted it and I got it.
Another Gen 3 one was when I first battled Steven (cause I had Emerald) he seemed like a true final boss and for some reason I just really remember that fight and was so into it.

The other one is the underground in Gen 4. Fucking best multiplayer ever. I would play for hours upon hours with my siblings and friends. Those were the good times.

Also I played XD with my friend and I loved that. He had an Espeon and I had an Umbreon and we went through the whole game like that.

1. Ash's Zs? Like... making yourself look like Ash?

2. Oh god, that happened to me once. I was in the E4 in Platinum or Diamond, I went out to play football/soccer with my friends, but one of them stayed back. Fucker stole my legendaries. How'd I know? When I turned on my game, I was a few rooms back in the E4.

Playing Pokémon Gold on the Gameboy Color and trying to play the game at night on a car using the street lights to see the game, discovering you can go to Kanto after beating the main game, the day/night cycles, making various kinds of Pokéballs, being able to catch both Ho-oh AND Lugia, that Lapras on a cave, trying to catch a shiny Ditto for hours, etc... I could talk about this game for days, so many memories xD

Pokémon Platinum was wonderful too, played it a lot with my friends and we spent a lot of time on those secret bases, competing to see who had the best one and mining for stones.

Other than these 2 games, the other Pokémon games didn't feel as good to me, recent ones have been pretty lackluster on content imo.

My fondest memories are likely when me and my friends Played Diamond and Pearl together in school, and traded pokemon, great times

My fondest memories of the franchises was trading Pokémon with my friends at school (and not so friends, just an unkown person who was with a GB). Those were marvelous times.