When I was a kid (7-12) I had this massive crossover/fanfic in my head, that I was the star of. It was just a huge running cross over of everything I like, jumbled into a single setting, with very little explanation of how it worked.
It started me as a 1/16th Saiyan, Jedi Master, Pokemon Master, Power Ranger, Spaceship Captain.
When I was 13-14, I "rebooted" and decided that it should be limited in the things it contained. So I cut it back to only include Stargate and Star Wars. Then I decided to included Warhammer 40k and the re-imagined Battlestar Galactica. Then I started including some of the more "realistic" things I liked, such as Bones and Skins.
Then I decided to included my own versions of the Marvel and DC universe. Then I just went fuck it and let things like Pokemon and Dragonball Z back in.
Currently my shared universe (it's actually more of a multiverse of multiverses, that I call an "Uberverse") includes the following
>Star Wars (PT, OT, my version of the old EU)
>Stargate
>Warhammer 40000
>Battlestar Galactica
>Firefly
>Spartacus: Blood and Sand
>A Song of Ice and Fire
>Pokemon
>Dragonball Z
>Marvel
>DC
>Transformers
>Doctor Who
>John Wick
>Castle
>Far Cry
>Halo
And I think there may be a few others I'm forgetting.
I'm still the main character and I still kick a shit load of ass. But I do attempt to make myself more rounded as a character.
I have no intention of ever releasing this for public viewing, it's just something I still work on for my own personal enjoyment.