Behind the Scenes of ‘Dancing With the Stars’ Season 21’s Last Rehearsal Before Premier

Inside the final rehearsal as the stars prepare for tonight's season premiere.

— -- Dancing stars and thousands of their fans are shutting down Hollywood Boulevard to tape tonight’s season 21 opener of “Dancing With the Stars.”

Irwin’s mom and brother were inside the ballroom, anxiously watching her last-minute rehearsal.

“One dance, one, one,” she said, remaining optimistic. “I’m so happy!”

Some of the stars are overwhelmed.

“It’s my first time here,” said Hayes Grier. “Yeah, it’s unreal.”

“This is crazy,” Alek Skarlatos added. “I mean, the lighting and the spotlights and all of the chairs.”

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The 13 couples have spent three weeks rehearsal tonight’s one dance.

“You know, you commit yourself 100 percent,” Tamar Braxton explained. “I believe in that.”

“That’s why we get along,” Braxton’s professional dancing partner, Val Chmerkovskiy, said.

Alexa and Carolos Penavega are the show’s first dancing married couple, competing against each other.

“We do sit in bed at night and watch videos of us dancing and their past dances,” said Carlos. “And we’re taking this very seriously.”

The Penavegas admit that, at rehearsals, they compare notes with their pro dance partners.

“We do have little pow wows where he’ll come in and see our routine and we’ll go in and check out his routine,” Alexa said.

“I just want to do the best I can for everyone that I love,” she said.

“My mom passed away six years ago,” said Andy Grammer. “Doing something like this show where I’m thinking about her every single day has been really sweet for me.”

Dance lessons are also turning into life lessons.

“Only because I cried,” she quipped in return.

“Basically, she treats me like a horse,” Espinoza joked.

“Every ten minutes is a different Gary,” he said.

“Dancing With the Stars" premieres tonight at 8 p.m., 7 Central on ABC.