My first ever Pokemon, my specialest boy of all time, Splasher. I transferred all of my Pokemon from my first game up to X when that came out, but the save file got corrupted and I lost everything. Genuinely very tragic, I mourned as if my real pets had died. Years later, I was fiddling around in PKHEX, looking at my first-ever save file (which had no Pokemon left on it)... and it turns out, a copy of Splasher was saved, because he was the last one to be "asleep" in Dreamworld!! I actually teared up when I saw him. Forever frozen in 2013.
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