I have a very spotty memory about my personal life, especially my teen years. But that post about middle school anime (and having to Google how old I would have been in 7th grade to figure out what year it was) got me wondering about the exact timeline of how I went from "gets into anime" to "realizes I'm trans." Thankfully I still remember most of the websites I used as a teen and my usernames so I was able to do some sleuthing and I think I've assembled the timeline of how my egg cracked.
1998: Pokemon debuts in America and a very young me is instantly hooked. This would lead to a lifeline obsession and also interest in such shows as Digimon and Monster Rancher.
2002: As I enter middle school, I learn the term anime for the shows I was really into as a kid. I begin actively seeking out anime and get into Yu Yu Hakusho and Inuyasha at around the same time. At the same time, puberty starts to rear its ugly head and while I can't put my finger on the why I am immensely uncomfortable with the changes happening to my body.
2004: As I begin to spend more time online I start getting into fanfic and make a fanfiction.net account. One day, while browsing Inuyasha fanfic I stumble upon an InuyashaxRanma 1/2 crossover. I look up what Ranma 1/2 is, and something clicks in my brain. I start getting really obsessed with stories where guys get turned into girls. I seek out fanfics and web comics about it.
2005: I make a Gaia Online account, with a male avatar.
2006: I change my Gaia avatar to a girl. I make a journal entry about this that's evasive about why. From my best recollection, this is about when my egg started cracking. I think at this point I'm still thinking of myself in terms of "A guy who wants to be a girl" and at least on Gaia I'm still referring to myself as [Dead name]
2007(?): Exact timeline is inexact because Super Smash Bros Brawl had a long pre release cycle, but during a joke topic on the GameFAQs message boards for Brawl I claim to be a girl. This is one of the first times I call myself a girl on the internet, and being called a girl and treated like a girl by others kind of shifts my internal self perception to "I am a girl" finally.
Honestly, there's something really comforting about being able to travel back down memory lane and hunt down my past online presence like this because just looking this stuff up helped me recall all this, and for someone who struggles to remember stuff from back then... it's nice.