I can only imagine how my confession would sound:
Me: Bless me, Father, for I have sinned. I wrote a scene where my Catholic dragon bit off a guy's hand. I did make him go to Confession--
Priest: A Catholic dragon?
Me: Oh, yeah. He's a good one. Only one head, no reference to Revelations, as he would say. The problem is, it's really a very funny scene--
Now a priest who is really in tune with me would say something pithy like, "You've got to hand it to him?" and I'd be laughing and having to confess all over again.
So I have to confess, I usually stick to the real-world sins and hope God understands about the flights of fancy.