Cast member Zacharias Harris, who plays Tiny Tim, claps to a song as he reherses a scene for "A Christmas Carol" at South Coast Repertory. (DON LEACH, Daily Pilot / November 16, 2012)

Audiences may notice a few new things in this year's production of Charles Dickens' "A Christmas Carol" at South Coast Repertory, but director John-David Keller promises there are no drastic changes.

"We can tweak it. We can't change it," said Keller, who's directed the play all 33 seasons at SCR. "We can make subtle things different. Our audience is 60% repeats; they'll notice the things we have done differently when first-timers certainly won't."

Those subtle changes include updates in some of the wording, some new music and a bit of a "surprise" with Jacob Marley, Keller said.

Keller believes it's comforting for people to know each season "A Christmas Carol" will be at SCR and not much different from last year or when it first opened in 1980.

"We are no longer just a play," he said. "We are a tradition. I think, more than any other time of the year, there's that longing to go back to tradition during this season."

"A Christmas Carol" opens at 7:30 p.m. Nov. 24 and runs through Christmas Eve. The most recognizable constant will be Hal Landon Jr., who will play Ebenezer Scrooge for the 33rd year.

Of course, there are some changes audiences can rely on — 16 to be exact. That's the number of the supporting roles for children and teenagers that are recast each year.

Thirteen-year-old Grayson Airth, a seventh-grader at Harbor Day School, had routinely seen the play with her family before being cast as a Young Girl and Want in this year's production.

"I have seen it almost every year, and it's really amazing to actually be in this huge production that a lot of families go and see every year," said Grayson, a Newport Beach resident.

Each year, about 80 children and young adults, who are 8 to 18 years old and enrolled in acting classes at the company's Theatre Conservatory program, audition for the 16 spots.

The most coveted role is that of Tiny Tim, played this year by 8-year-olds Zacharias Harris and Hadley Belle Miller. Zacharias and Hadley reside in Corona del Mar and Huntington Beach, respectively.

Zacharias, a third-grader at Harbor View Elementary, was honored to be cast in the play at all, let alone in one of the lead roles.

"I was a little surprised," he said. "Like, 80 kids try out and only 16 are picked."

While there were plenty of nerves involved for the kids, Keller said choosing the next Tiny Tim has gotten easier each year he directs "A Christmas Carol."

"The longer you see actors, the more you know pretty quickly this is the person I'm looking for," Keller said. "I don't know what it is about them, but I just know."

Once cast, the group is divided between the Red and Green teams. The squads rotate productions on alternating days and nights to allow the young actors to juggle a busy schedule of school and rehearsals, which began Nov. 1 and are usually held six days a week.

"I have learned that you have to have a lot of teamwork [to be an actor] because all of us rely on each other," said Abby Matzke, a 12-year-old Huntington Beach resident and Pegasus School student, who plays Belinda Cratchit and a Rich Girl this year. "You have to be able to trust other people."

Along with Abby and Hadley, Sebastian Naranjo is also a Huntington Beach resident. The 10-year-old St. Bonaventure School student realized he wanted to be a movie star when he went to see "A Christmas Carol" at SCR with his family.

"I thought, 'Wow, one day I want to be there performing that play,'" Sebastian said. "A year later, I'm in it."

Grayson also strives to be a professional actor one day. She hopes "A Christmas Carol" is her first of many big breaks.

"I have learned everything about acting here, because I hadn't ever really been through a professional process," Grayson said.

For the veterans of "A Christmas Carol," it's that sort of excitement that helps keep everything new after more than three decades of putting on the same production.

"The thing that keeps it fresh are the kids," Keller said. "They are truly wonderful. Their excitement and enthusiasm is invigorating."

andrew.shortall@latimes.com

Twitter: @TCNShortall

If You Go

What: "A Christmas Carol," adapted by Jerry Patch from the story by Charles Dickens and directed by John-David Keller

Where: South Coast Repertory, 655 Town Center Drive, Costa Mesa

When: Opens Nov. 24 and runs through Dec. 24. Performances are Tuesday through Sunday with times ranging from 11:30 a.m. to 7:30 p.m. depending on the day.

Cost: $26 to $63 with discounts available for students, seniors, those under 25, educators and groups

Information: (714) 708-5555 or http://www.scr.org