Last week, while watching Season 2 of The Ghost Whisperer, I was struck by a thought on character chemistry. See, season 2 introduced Professor Rick Payne, played by Jay Mohr. Payne was supposed to be a character brought in for a short story arc and nothing else. But there was a problem. When Mohr and Love Hewitt were on the screen together, there was immediate, obvious, and fantastic chemistry between the characters. It was apparent to me as the viewer, and from the interviews I watched on the special features, it was apparent to the cast and crew as well.
So they brought him back. And I found myself looking forward to every episode he was in. I knew that every time he showed up on screen, the show got that much better. The funny thing is, after a few episodes, I was telling my husband how there was so much more energy between those two characters, how there was this slight sexual tension, even though Melinda Gordan was very happily married, and how her relationship with Payne was something she needed to contrast the relationship with her husband (who, let's face it, is a gorgeous lunkhead). The beautiful David Conrad isn't nearly as fun to watch on the screen as Jay Mohr, whose smile simply lights up the room. And then I watched the interviews with the cast and crew, and they said exactly the same things I'd been saying. That's how obvious it was from the viewer's side. The chemistry between Melinda Gordan and Rick Payne was "it."
Like porn, "it" is hard to define, but you know it when you see it. It's not necessarily sexual. In fact, in my latest book, I have a lot of chemistry between my heroine and her twin brother. It's definitely not sexual with them (ew!) but it is very real.
So how do you create real chemistry between your characters?
You can't. You won't even know you have it until you throw the characters together and see how they react. Some of the characters you thought would have real chemistry together don't. I had planned on my heroine having it with a former classmate she'd had a crush on. Turns out there was nothing there, but another character I never even expected grew into the one. All you can do is watch for it as you're writing. When it happens, go with it. Not all your characters will have this strong chemistry together. That's fine. They'll still be good characters to throw together. But keep a watch out of those characters who "pop" off the page. when they're together. The more of them you have, the better your story will be.