The Voices in my Head.
They come up with some pretty interesting stuff.
Like, how to use "like" in a sentence properly, if you, like, grew up in, like, that decade that was like, a couple decades ago.
They also have this thing going in a New Adult novel where an assassin and an unaware innocent meet and fall in love and overcome all kinds of odds and emotional dysfunctions to make things work, except get this: the assassin is the girl!
Actually, I might get cracking on that one.