NEW YORK - Think of Hugh Laurie in his role as Dr. House. Or William Petersen as Gil Grissom. Or America Ferrera as Ugly Betty.
On the other hand, why think about it? When an actor's perfect in a role it's obvious, so obvious as to feel inevitable, and so inevitable the audience forgets that anybody had to intervene to match the actor with the role in the first place.
Casting is an enterprise whose success is confirmed only in hindsight, once viewers have embraced the casting choice as destiny.
The best casting is invisible. So how hard could it be to pull off?
Turns out it can be tricky. It's a process of discovery mixed with prescience. Gut instinct is important. So is deep knowledge of the churning talent pool. You have to recognize which actor is right for the part. You have to get the actor signed. But first, you have to know the actor exists.
"The key to casting is information," says Marc Hirschfeld. "To be a repository for information: Everything Actors!"
Otherwise? "You'll miss someone."
Hirschfeld is executive vice president of casting for NBC Universal Television, where he oversees casting for the NBC network and other NBC Entertainment programming.
Earlier in his career, he co-founded a company responsible for casting such series as "The Larry Sanders Show," "3rd Rock from the Sun," "Party of Five," and "Seinfeld."
Before that, "Married . . . with Children" was developed for Sam Kinison and Roseanne Barr. But they both passed. Hirschfeld, searching for actors who could save the project, thought of an unknown named Ed O'Neill, whom he'd seen on stage in the decidedly uncomic "Of Mice and Men." O'Neill was perfect as the doltish family man Al Bundy. "Married" became the Fox network's first breakout comedy.
In 1999, Hirschfeld joined NBC Universal, where he describes his job as threefold.
First, to serve as a lookout, "identifying talent I think we should be in business with, and make overall deals with them." (Item: Lauren Graham, perfect for seven seasons on her CW hit "Gilmore Girls," signed a development deal last month.)
He also supervises casting for current shows. (Did you happen to notice Jerry Seinfeld's wildly hyped guest shot on the season premiere of "30 Rock"?)
And he looks ahead to comedy and drama projects in the pipeline, anticipating what their casting needs might be.
"I make lists of names. I'm constantly talking to agents to see who's available, who's not available, who's considering TV this year. Meeting with actors, looking at tapes. Always putting together ideas."
Hirschfeld and his staff of a dozen attend film festivals and comedy clubs, troll the Internet, and even monitor podcasts.
They also draw on a long memory.
Hirschfeld tells of a child actress he cast in a pilot that didn't sell five or six years ago. He kept his eye on her career after that. Flash forward to early 2006, with the casting for "Heroes" underway.
"When they were trying to decide who the cheerleader should be, I literally picked up the phone and said to the producers, 'You got to meet Hayden Panettiere,' " he recalls.
More recently, he screened an audition tape from a young London-based actress. He wasn't familiar with her. She had masked her accent on the tape, "so I didn't even know she was British. I thought she was an American living in Britain."
He sent her tape to the producers then trying to fill the all-important title role for their prospective series, "Bionic Woman."
But Michelle Ryan didn't instantly win over the producers.
Nor was she sure she would want to do the show anyway. She had just finished six years on the long-running British soap opera "EastEnders," and had cold feet about another lengthy series commitment.
So Hirschfeld flew Ryan to Los Angeles to meet with the producers and NBC brass. She shot a formal test. They offered her the role. She accepted it.
"Marc was very much about not taking no for an answer from Michelle," says Katherine Pope, now president of Universal Media Studios, then a NBC drama development exec. "And he was very much about talking to the producers about why she was the right choice."
"It's really the producers' decision," says Hirschfeld, who says he knows not to push too hard: The people running the show have to be inspired by the actor to write a part that comes alive week after week.
He also knows not to push his boss too hard. As Hirschfeld explains, the network president has got to be excited about a pilot to take it to series, and if he's less than thrilled about an actor chosen for it, that pilot may never get his go-ahead.
"I'm just one voice among many," Hirschfeld insists. "This is a business of collaboration. But I've been doing this long enough where - not every time, but often - I have a pretty good sense if an actor is in the zone and it's worth exploring further."