I've been a Godzilla fan for since I started watching TV. Don't know when was that. I think the Godzilla movies I first saw were 98-Zilla, GMK, G2000, Final Wars, GxMG, and the American version of Gojira.
I have also been watching the entire Jurassic Park series as well as the MCU, the Star Wars trilogies, some DC movies.Why did I start writing fanfiction? Well first I began writing them in notebooks which I still do.
Well, when I started I was writing a story about what happened after Jurassic World. It didn't sound that bad at first and then I wrote what I called "The Monster Squad" it was a crossover series between HTTYD Godzilla Gamera King Kong Batman Wolverine Iron Man. It felt like a good idea but I realized that I didn't have any have any explanations for the whole thing. Like:
How did Toothless and Hookfang end up in Modern times?
How is Monster X's daughter a Night Fury?
How does Wolverine Batman and Iron Man fit into all this? 
Imagination is crazy when you are in 5th grade.
I abandoned both the Jurassic Park and the Monster Squad fanfictions for a while. Then last year during the summer I began writing a Godzilla-Pacific Rim-TMNT-DEADPOOL-Wolverine crossover. Inspired by a couple of fanfics I read.
I'd say that at the beginning of this year or so I began reading RWBY fanfic. This month or so I watched the first volume of the series on Vudu and I thought it was a great idea to write a crossover fanfic or more.