I finally found the account name of the person whose music I saw without signing in back in 2009, which effectively was my first time stepping into Newgrounds. That user's name is @ForbiddenMemory.
@CaptKirky did quite a bit of prompting to me when we spoke with each other over my earliest memories of NG, and somehow, I went to Wikia, which is where ForbiddenMemory and I met under different usernames. I knew that he had music of his own, and so I looked up his links. His Newgrounds page was listed, and I saw The Icy Lands, the very first music track I listened to on here. See, seven years ago the two of us were part of a Kingdom Hearts fanon project, and we imagined up our own characters and our own background music based on what we'd learnt from the few games released then -- KH1, Chain of Memories and KH2. Shortly after listening to his work, he pointed me to @TheWeebl, which then pointed me to Weebl's Stuff.
It took me 7 years, but now I finally remember. Time to update all those statements, forum posts and interviews where I completely forgot who it was that brought me to NG first.
Template88
Couldnt've been easy to do. I had a similar experience trying to find "a ball" animation that i had seen when I first saw newgrounds.
Troisnyx
Initially it wasn't, because the Kingdom Hearts Wiki where we'd contributed had split into a bunch of sister wikis. One got its own domain, while the rest stayed within Wikia. This friend hadn't been there during the time of the split. We carried all content over from Wikia to the new domain, everything except user pages. For years I'd tried to find this person's username, but couldn't.
Don't know what made me want to search Wikia again. But somehow, by some miracle, I managed to find his name.
Do you remember what this ball animation looks like? I could join in the search, if you'd like.