Stephenson (25) will play Chad, the leather-jacketed, tight-jeans-wearing, guitar-playing rebel who rides into 1950s small-town America and shakes up the locals, all while singing the hits of Elvis Presley.
Stephenson features in all but two scenes and sings 14 songs, not including tunes where he sings backing vocals.
While he has entertained by singing and playing piano most of his life, his only previous musical theatre experience was playing Louis in a Sydney high school production of The King and I, at the age of 14.
"It's a big role and a big responsibility, but it's one I'm relishing," he said.
Chad was "a very enjoyable fellow to play. He's a very cool, confident character. At least he starts out that way, and throughout the show you see the facade cracking.
"You could compare him to Danny, from Grease, or The Fonz."
Stephenson only heard about the auditions on the day they were being held in Queenstown and drove straight from his parents' home in Invercargill to try out for the role.
He was given two Elvis songs which Chad sings in the show, If I Can Dream, from the '68 Comeback Special TV show, and I Don't Want To from the 1962 movie Girls, Girls, Girls!.
Although he was expecting a call back in a few days, Stephenson was told he had the role the same night.
"I was elated, ecstatic. I was standing in a bar with people I didn't know and pretty much jumped for joy."
Rehearsals involved layering the part, by learning the music, then the plotting and movement, under the guidance of musical director Cheryl Collie, director Bryan Aitken and choreographer Tiffany Menzies.
Rehearsals have now moved to the Queenstown Memorial Hall, where All Shook Up will be staged from May 19 to 28.
Stephenson plays piano part-time on board the steamship Earnslaw, as well as in other venues in Queenstown and Invercargill.
The first cassette he ever owned was by Elvis and he has been a fan since.
"People will love the new interpretations of classic songs. It's a show to sing along to and hopefully they'll be dancing in the aisles. You'll leave feeling better than when you came in."
