It's the unexpected third member of Potted Potter who makes the show.
The Unauthorised Harry Experience features Gary Trainor and Jesse Briton. Trainor plays Harry and Briton is everyone else in the seven Harry Potter books in 70 minutes.
Then there is the audience, young and old, heckling, shouting comments and helping with a live Quidditch match.
Four hours after the show, Trainor and Briton are still laughing about the man who stood up to yell ''blasphemy'' when Trainor dared to suggest Harry was boring as a character.
''We do like to encourage anarchy,'' Briton says, admitting he thinks the show is best when it's falling apart.
''Yeah, the audience can steal the show,'' Trainor agrees.
The little boy in the 10th row who calls out ''He's behind you'', when Harry is supposedly looking for the One whose name shall not be mentioned, sends the audience and both actors into gales of laughter for several minutes.
The show is supposed to be a parody, but it's very close to English pantomime in the best sense.
There is a risk in a show like this. Fanatical fans can be cruel about shows that take off their beloved fandom, but Briton points out that it's not really about sending it up.
''The fans have been wonderful. They seem to be up for it,'' he says.
Originally performed by its creators, Daniel Clarkson and Jefferson Turner, as a five-minute sketch to summarise the plot of the first five books as entertainment for fans awaiting the release of the sixth book, it grew into a hit at the Edinburgh Fringe and then became an award-winning West End show. Trainor and Briton are the touring cast.
It condenses all seven books into 70 irreverent minutes. It's an epic task, Trainor admits, and he thinks it succeeds on different levels, enough for children and adults to enjoy it in different ways.
Fifteen minutes before the start, Briton is in the audience, talking to children, making them grin, while Trainor sits on stage reading one of the books.
There's a slow start, a voiceover and a setup that seems to take a while, before they get into the first book, but once there, the show races through the books.
The props are intentionally minimal, Dobby the House Elf is adorable and Briton is a goofy version of all the characters he has to pull together.
You get to play Quidditch, with members of the audience called on to be seekers, and children leap at the chance.
Somehow they manage to get their own version of Gloria Gaynor's I will Survive in there and have it work.
Take the children. Enjoy it on their level. An audience of adults would over-think the show.
''Wear costumes and bring wands,'' Trainor says.
He is a massive Harry Potter fan and grew up reading the books.
''There's a dark element to the books, even though they are for kids, that Rowling does really well,'' he says.
He has favourite characters, Luna Lovegood and Hagrid, while Briton is fond of Remus Lupin (he's a huge fan of David Thewlis, who played the character on screen) and Ron Weasley.
''He's just like a typical English schoolboy, whose mother knits him sweaters and his best mate happens to be like Brad Pitt.'' Briton says.
They have both been touring the show in Asia. They were a bit apprehensive about how it might be received. but all was well.
''The fans are everywhere,'' Trainor says.
They are looking forward to New Zealand for the first time.
Trainor would have come already if his agent had got him an audition as a hobbit.
''I really, really wanted to be a hobbit,'' he admits.
Deborah Morris was flown to Sydney by the show's promoters.
- Potted Potter, Opera House, Wellington, October 31 until November 4.
- © Fairfax NZ News