Photo © Robyn Bacon

Matt Stone and Trey Parker worked on The Book of Mormon for seven years. One Night Only: The Greatest Musical Never Written achieves greatness in one night – with no script, no pre-planned choreography, and no clue what the show will be about until the audience tells them.

Created by Alan Kliffer and directed by Melody Johnson, One Night Only is the most ambitious improv spectacle I’ve seen in a decade. When cast member Jan Caruana nudged an audience member who was slow to give a suggestion, saying “It’s a two-hour show,” I thought she was joking.

As the show progressed – the night I went was dubbed “Nerd Alert: The Musical” – it seemed impossible that they could keep the energy, laughs, and all those improvised balls in the air for a second act.

How wrong I was.

The talented cast of Ashley Botting, Jan Caruana, Reid Janisse, Carly Heffernan, Ron Pederson and Alex Tindal performed like a well-oiled machine: one that was being built right before our eyes.

Unlike most improv shows where everything’s mimed, the characters were enhanced with a few well-chosen props. My favourite was Reid Janisse’s fluttering lace fan – a hilarious counterpoint to his Randall character’s menacing megalomania.

The story revolved around Caruana as Linda Johanssen a.k.a. Debbie Dynamite and Pederson as her long-lost love, Gavin. Botting and Janisse played Equestria and Stable Boy (a.k.a. Randall), Dynamite’s rivals who eventually leave show biz for horseplay of a different kind.

Scenes were punchy and playful, culminating in a show-stopping number where all six players came together for a song called “More,” made all the more awe-inspiring for its on-the-spot harmonies.

Special props must go to the orchestra. With back-up vocals from Kevin Vidal and Miriam Drysdale, musicians Ewan Divitt, Jake Koffman, Dave Stein, and Justin Han were every bit as (forgive me) instrumental in the creation of what happened on stage.

Besides their musical chops, they knew just when to cue the next number, and were clearly having fun with the cast. While Ashley Botting’s pipes never fail to astound, it was Ron Pederson who stole show after being badgered into one more solo by the band.

One Night Only has been playing to packed houses, and runs until February 14. Avoid disappointment; book now.