About 9-10 years ago I was in 7th grade, 11-12 years old, searching the internet for stuff on Sailor Moon. Yes, Sailor Moon.
And then I discovered something called "fanfiction". I don't joke when I say I got most of my sex-ed from fanfic. Yea, I know, shocking to most, but I turned out pretty OK if you ask me (in no way condoning children reading smut, just giving my personal experience)
Back to the point, at the time I thought Sailor Moon fanfic was the King of AU. All the Serena's suddenly became clumsy but strong, independent, and usually pretty smart. Darien became either cold and depressed or cocky...and depressed....Seeing an iteresting comparison yet? No, not saying anything was plagiarized so get that idea out of your head now, just thinking how interesting it is how similar an AU can be whether it be Sailor Moon, or Twilight.
10 years later and I'm thinking up stories for Edward and Bella that seem oddly familiar to me...and then it dawns on me that it's because I already read them with Darien and Serena (or Mamaru and Usagi if you wanna go all proper with me).
I've read fanfiction for PLENTY of other fandoms, but nothing comes as similar to Sailor Moon to Twilight. Probably the epic love and all that jazz.
What was your first fandom? How old were you? Can you find similarities between the fandoms?