There’s a scene in the movie “Young Frankenstein” in which Igor is sent to get a brain for the creature being created back in the lab. He sneaks into the local brain repository and finds the one he was sent for, that of a brilliant scientist and humanitarian who had just died. However, startled by a flash of lightning, he drops the brain and smashes it. Igor, not the brightest bulb on the Christmas tree, takes another brain, one marked “ABNORMAL: DO NOT USE THIS BRAIN”. The creature is born a monster instead of the pinnacle of perfected humanity.
So, yeah, it’s like that when you’re creating a character. If the creature had gotten the right brain, he would have been much less interesting. Somewhere in the background of your character, someone misread a label and shoved a messed up brain into a perfectly good body.
Or maybe it was a bad liver. Yes, that’s it, a bad liver. Which is why your character gets drunk so easily, because she lacks a functioning version of the alcohol dehydrogenase gene. That lightweight tendency is what led her to that unfortunate experience after the junior prom, when she tried her first rum and coke. That jerk boyfriend of hers saw an opportunity, and he…
Or maybe it was a bad set of teeth. Of course! His crooked teeth made him socially awkward, not so much because of the looks, but because they advertised to all his classmates that his parents were too poor to afford braces. He wasn’t a bad kid, but feeling like an outsider made him act like one, and then, when the bullying turned nasty, why, he just snapped from the accumulated burden of taunts and insults. It wasn’t his fault that the chainsaw practically started itself…
Lest my tortured “bad organ” metaphor die a painful death before it can beg for mercy, I’ll abandon it and say that whole, complete, properly functioning characters are boring. Flaws are interesting. Deep flaws make for even more interesting characters. Sometimes the interest is in the character’s struggle to overcome them; sometimes it arises from the character’s inability to even see their own flaws, or recognize them when they are pointed out. Mr. Darcy’s blindness to his own pomposity makes him infuriating in the middle of “Pride and Prejudice”. Inspector Clouseau is funny in large part because he doesn’t realize he’s an idiot.
Even when people have abilities and gifts that lift them well above normal, they can still be boring without any flaws. A smooth, supremely capable superhero/secret agent/trial lawyer/detective/whatever is MUCH more interesting if he gets his hat handed to him every once in a while. Think Roger Moore’s 007 vs. Daniel Craig’s 007.
Let’s take two completely normal people: John and Denise. They’re both fine, reasonably happy, reasonably well-adjusted people with no major flaws. Pretty boring, right? You can give one or both of them some flaws and let them play it out. Give her a gambling addiction. Make him stubbornly refuse that he’s lactose intolerant. Have her get hit by a meteorite and him try to capitalize on the publicity.
But do you have to give them flaws? What if their very normalcy is itself a flaw? Can you do that? Sure!
A deranged serial killer breaks into John and Denise’s isolated vacation home and takes them both prisoner. Suddenly, John’s hobby of birdwatching instead of gun collecting is a big problem! Denise’s ballet classes, once perfectly fine, now look like a really lousy alternative to taekwondo.
However, check this out: At a crucial moment, Denise is given the opportunity to snap from a second position down into a plie, thereby flipping the serial killer over the railing and onto the rocks below. However, since she’s been kind of half-assed about her ballet, she isn’t in shape so as to do a proper plie, so when she tries, not only does the killer not go all the way over the railing, but her Achilles tendon tears and now she can’t run away from the killer.
John, having gotten free of his ropes, uses his big, heavy binoculars, the ones with the Zeiss lenses, as a weapon to bludgeon the killer. However, because they were a gift from his father, from whom he learned to love birding in the first place, he pulls up at the last-minute and misses.
And so on….
There’s nothing terribly interesting about someone who takes ballet, or someone who engages in a hobby because it reminds him of his father. These aren’t flaws… unless the circumstances are such that it becomes a significant aspect of the character, something that drives the plot forward. Instead of changing the character to make them interesting, you can change the circumstances. Make your boring character a fish out of water, and they become better characters as they try to adapt and respond.
So go ahead – stick that weird brain into the lifeless body on the slab. That’s where the best monsters come from.