Okay, what you're gonna wanna do is take a large frying pan (preferably iron, but any kind will do) and repeatedly hit yourself in the head so that your motor skills are temporarily disabled. Now be careful! If you hit yourself too hard or too many times, your motor skills may not come back and you'll be stuck in a semi vegetable state. You'll also want to study the human brain a bit before hand so you'll know precisely where to hit so that you don't accidentally grant yourself psychic powers somehow. Sure it seems fun at first, but after the first couple of heads accidentally explode, completely ruining my tux and making Sally Winfield run away from me at prom it loses its appeal.
Either way, after you've achieved the desired level of mind numbing stupor, you can then proceed to randomly select the fictional creature that you wish to ruin completely. I would suggest Frankenstein's Monster or a Rhode Islander (c'mon, who here knows anyone who's ever been to or knows someone else who's been to Rhode Island? Exactly! It's a fictional place), neither of which are commonly depicted in horrible romance novels.
Once you have your monster selected, you'll need a Mary Sue. Now, you're gonna want to at least vaguely appear like you've attempted to make the character an actual character. To subtly hide the character's perfection, you should pretend there's some kind of flaw to the character which you should bring up frequently, but never show. Y'see, readers are like wild animals. If they see weakness, they'll attack and kill your avatar. Readers are the one thing capable of killing your character. How they do this can't be explained, know only that they do. To avoid this, you should only feign weakness lest your character fall to their might.
Y'see, the story is only half about ruining a mythical creature by making it a teenager. The other half is protecting your avatar. To do this, you should slip in some kind of hypnotic subliminal message on the cover that will target adolescent females making them into a formidable army. In this way, your army of zombie fangirls will rise up in your defense whenever your character is attacked, with deadly consequences. Your hypnosis will also allow you to have an increase in sells. But that's more of a side effect, really.
Now, with this knowledge go forth and conquer the world of literacy.