It was a little while after I'd discovered GBA emulation, from what I remember. I found Whack a Hack in my search for Pokemon roms, and from there I learned about rom hacks, then downloaded and played my first rom hack ever, Pokemon Quartz (which I believe had been completed not long after I first visited the site).
Afterwards, I played a few others I managed to find, including obscure ones like Pokemon Dragonstone and Pokemon Iolite. The one that inspired me to try it myself, however, was Pokemon Shiny Gold. I really liked how far you could take a standard Pokemon rom and turn it into something else entirely.
So then I learned whatever I could about rom hacking, striving to make one myself. I remember one of my earliest attempts being a rom hack of Ruby set in the Sinnoh region, with its own PHO/TPB thread and everything. I scrapped it tho when I learned how much work was actually needed to remake the entirety of the Sinnoh region lol. That was years ago, and since then I think I've learned a lot more, enough to finally kick off a new project of my own. Now if only I wasn't so lazy