If you are currently wrapped up in a cuddle pony blanket.. (funny enough I didn't even think of that at first... was in the middle of contemplating what to post, happened to look away from the screen and.... well here I am now)
you may be a brony when all of your made up characters inside your head start to look like ponies or turn into ponies.
You've brought Twilight Sparkle plush/figures to class because the real Twilight Sparkle would enjoy it.