ST. LOUIS (AP) ¿ With her hair neatly pulled back in a dancer's bun, a gym bag of exercise clothes by her side, eight-year-old Morgan Fritz is ready to talk about her role in "The Nutcracker''.

Her father Ron has lifted her off a device called a Standing Dani, a system similar to a wheelchair but one that allows her to stand up and be mobile. He places her in a seat at the Fox Theatre before rehearsal begins.

"My body is weak all over. I can't walk," Morgan says. She has spinal muscular atrophy, a genetic disorder that destroys the nerves controlling voluntary muscle movement.

She has discovered, however, that she can dance.

The Chicago-based Joffrey Ballet, in a company tradition, includes disabled children in its holiday productions of the iconic ballet. The entire production has been double cast, so the many children involved take turns in performances. Morgan and another disabled child, 11-year-old Libby Schueddig, share a role that they've rehearsed on weekends with the other kids.

"It's fun, and when I'm having fun, I don't get tired," Morgan says.

Charthel Arthur, a ballet master for the Joffrey, said a disabled boy saw a 1995 summer dance performance involving people in wheelchairs. Inspired, the boy showed up later that year when the company held open auditions for its holiday production. He was cast in a role in the act one party scene. The unconventional casting of "chair dancers" ¿ children in wheelchairs ¿ for the role of "Party Boy No. 8" in the Joffrey's "Nutcracker" has continued.

In the St. Louis performances, which began on Wednesday, Morgan and Libby have rehearsed to the point that they look like veterans. Schueddig has spina bifida, a congenital defect in which the spinal column fails to close properly.

The girls don't dwell on the logistics of being in a ballet while in a wheelchair. Rather, each is excited about appearing on stage with professional dancers. Both are caught up with the fact that they are girls portraying boys, but explain that a lot of other girls are also playing boys. A quick glance around the lavish theater, where young female dancers in their black rehearsal leotards and white tights greatly outnumber the guys, makes it clear why.

Libby shows how she has practiced for the part, counting the beats of music and moving her head and arms in time. Onstage, the girls are among dozens of area children taking part, a little entranced by the family parlor set decorated to celebrate Christmas, and the Joffrey dancers who make their complex steps and lifts look effortless.

The girls sit in a wheelchair designed to look like one from the 1850s, the time when this Tchaikovsky ballet is set.

Can Morgan tell the story of "The Nutcracker"?

"Kind of," she says.

"Fritz and Clara have a big party at their house. She gets a nutcracker and then her brother Fritz smashes it. Then she gets sad. Then, she sleeps on the floor. Then she has this dream about her nutcracker and she goes in this world where there's a fairy, I think, who guides her through this world. She meets a lot of people. The Mouse King and the Nutcracker have a fight. Then, the Nutcracker turns into a prince."

Clara's godfather in the ballet, Drosselmeyer, is a toy maker and magician who gives her the nutcracker who magically leads her on her adventures.

Libby notes, "At the end of the party scene, Mr. Drosselmeyer takes glitter and sprinkles it on the chair dancer."

Assistant ballet master and dancer Willy Shives, 46, who portrays Drosselmeyer at this rehearsal, says the company's co-founder, Gerald Arpino, choreographed that moment as a special one for the disabled child in each production.

Shives and Arthur say the children in wheelchairs are always considered dancers in the ballet.

Shives points out that everyone has limitations. When he's raising a partner in a lift, her feet can't touch the ground, he noted. He credits Arpino for the unconventional casting, "for bringing this in, and opening our eyes to those that can't stand on their own feet," he says.

"They have their own way of expressing their artistry," Shives says. "We all have different ways of dancing."

The Joffrey Ballet's "Nutcracker" runs at the Fox through December 9 before opening December 12 at the Auditorium Theatre of Roosevelt University in Chicago.