As well as the cast, the show includes an orchestra and also makes use of the Opera House's revolving stage.
"There's singing, there's acting, there's dancing - and there's comedy as well, which is the hardest of all to do. But it is an incredibly funny show. Sometimes I have trouble focusing at rehearsals because I'm laughing so hard," Ms Nijsse said.
Jonathon Greenwell is the show's musical director and as such is responsible for organising the music and conducting the orchestra during the show.
He said the role was "full on".
"There's about 10 minutes of the show where there is no music. I have to be really on to it for the entire show," Mr Greenwell said.
The orchestra was put together especially for the show.
Making sure the cast know their steps is the role of choreographer Sarah Hylton.
Unlike the music and the script the choreography is not laid out, but there are guidelines, Ms Hylton said. Her role is challenging because of the lack of trained dancers in the show.
Ms Nijsse, Mr Greenwell and Ms Hylton all have to work closely together to ensure the show is just right. With opening night just a few weeks away, the show is in its "final layers", Ms Nijsse said.
"The final three weeks before a show can be pretty furious.
"We've been rehearsing four nights a week for a while now, plus extra rehearsals as needed.
"It's a big commitment."
The New Mel Brooks Musical Young Frankenstein will play at the Royal Wanganui Opera House on July 12, 18, 19, 20, 23, 24, 25 and 26. Adult tickets cost $45 and you can book at the Royal Wanganui Opera House or online at www.royaloperahouse.co.nz