Sitting in front of a dressing-room mirror at the Ordway Center, Jacquelyn Piro Donovan flits her eyes and opens her mouth wide to stretch her facial muscles. She is in the midst of physical and psychic preparations to go onstage as two characters central to “The Wizard of Oz”: the Wicked Witch and bicycle-riding Miss Gulch.

A handsome Broadway veteran, Piro Donovan is becoming a scary sorcerer. She is about to get an angled look with features that suggest the hooked jaw of spawning salmon.

Hair and makeup artist Michael A. King paints dark triangles above her eyelids. He next draws big, black Spock-like eyebrows on her forehead. He then adds two prominent prosthetic parts — a Jay Leno-sized chin and the long nose.

These physical features are only part of what she uses to portray her characters. Piro Donovan has a secret weapon that friends back home in Boston used to tease her about: her voice. Her laughter is a billowy cackling that begins at her knees and rises like a personal volcano, lofting joy and mischief into the air. The sound that comes naturally to her also is a perfect fit for the witch, a character she has fun with.

“It’s just my natural laugh, jacked up,” she said of vocalizations that have been so effective that they have frightened children.

“In Vancouver, this poor girl was crying so hard,” she said. “I very gently told her that I’m really not like that.”

Backstage beehive

While the audience settles into the Ordway, backstage looks like a beehive. Fog machines are being tested. Stagehands maneuver set pieces into place, rolling the yellow brick road on stage and off. Other workers spread out Glinda’s arrival dress, a spectacular blue curtain that will later wow the audience even as it serves a dual purpose of covering up a scene change. All of this activity by actors, makeup artists and stagehands is to make sure that everything goes off without a hitch for the Ordway’s big holiday show.

Piro Donovan is the only American in the 28-person cast for this new version of “Oz” — a production adapted by composer Andrew Lloyd Webber and director Jeremy Sams. It seamlessly melds Harold Arlen’s music from the 1939 MGM film with new tunes by Lloyd Webber in a show that originated in Canada.

Danielle Wade, who plays Dorothy, is like Canada’s version of Eagan-bred Broadway star Laura Osnes. She won a reality TV show competition — and became a star — for the part.

But the sweet-voiced singer does not have any airs as she walks into Piro Donovan’s dressing room in her character’s blue gingham dress and with a toothbrush in her mouth. When asked how’s it going, she gives a thumbs up to indicate that she enjoys playing the girl from Kansas who gets transported to Oz in a tornado.

“Oz,” which takes seven semitrucks to transport, has been on the road for months. While director Sams does not travel with the show, production stage manager Michael McGoff serves as his eyes and ears, and is tasked with keeping the show in tiptop shape.

On this day, he has notes for actors as he visits their dressing rooms half an hour before curtain. He compliments Jay Brazeau, who plays the Wizard, then offers some suggestions.

“Take your time with transition,” he said. “Don’t rush it.”

It’s 15 minutes before showtime, and the chatter of patrons is becoming louder as light cues are tested. Behind the curtain, actors and dancers mingle all over the stage floor, bathed in a hazy blue light. Some stretch, others seem to meditate.

The trainer for Loki, the understudy dog that plays Toto, also is onstage. He’s getting Loki familiarized with the actors the pooch will work with. Loki is calm, and experienced; he played Toto two years ago in a memorable production of “Oz” at the Children’s Theatre.

In the orchestra pit, musical director David Andrews Rogers is warming up his 10 players — half of whom were picked up in the Twin Cities. A few children have come to see the musicians.

“By intermission, they will swarm the orchestra,” said Rogers. “They will be curious about the music and the magic. This is what it’s all about — seeing them is the best part.”

The house lights dim. All the actors are in place. Rogers raises his baton, then launches into the overture. It’s showtime for “Oz.”