Three years on, the demand for the show continues, but Clarkson and Turner needed a break, so a casting call went out to find two equally entertaining replacements.
"I think mainly they were looking for people who were quite similar to themselves," laughs Trainor.
The pair, who'd never met before, auditioned separately first, and then together to test whether they had the all-important duo dynamic that is required.
"The show relies so much upon having an off-the-cuff relationship between the two parts, where you can feel free to play around, quickly and easily, so it was great to find the partnership between Gary and I worked," Briton explains.
Though the show is scripted and directed like a regular theatre production, Potted Potter also requires improvisation, audience interaction, and above all, an ability to convince everyone they're almost making it up as they go.
"Dan and Jeff watched the audition process and watched how we improvised, and I guess you can kind of tell if someone has the right improvisational quality," Briton adds.
"You know, whether there are appropriate things coming off the top of their head for a Harry Potter show."
It is family entertainment after all, and Briton and Trainor manage the comedic needs of an audience that often ranges in age between 6 and 60, by employing slapstick and physical humour as much as scripted gags, with inspiration from Monty Python and Charlie Chaplin. Briton gets to play the enthusiastic, innocent, goofball while Trainor is the uptight Potter expert.
"I see my character as being the straight guy for Jesse to dance around," Trainor explains.
He's also the Potter expert in real life, having read all the books multiple times, though both of them are long-time fans, which comes in handy when trying to keep all the storylines straight while they're leaping about on stage at a very rapid pace.
"I think the biggest challenge when we were learning it, was keeping in your head where the hell where you were up to, and keeping the continuity," Trainor explains. "For me, I think it's the changing between different characters in different books for different bits," Briton laughs, noting a few times when things have gone awry. "I've run on before in completely the wrong costume, I've also literally blanked. I did one show where I ran on and did a bit that we'd already done 20 minutes earlier! Luckily it's a crazy show, and the audience sort of expect it, and I get to clown around and improvise.
"It doesn't really matter," Trainor adds, "because it's actually funny to break out of it, and take the mickey out of each other."
Indeed, it's a show where the "fourth wall' - as it's known in theatre - between the actors on stage and the audience crumbles.
Briton always comes out and walks among the audience before the show begins, chatting to various fans before jumping back on stage, and the dialogue is often a direct conversation with the crowd. Plus people are invited to shout out and participate, and there's a live quidditch match that involves the whole audience.
It's one of Briton's favourite parts of the show, because it's entirely improvised and very unpredictable - he has to find various people in the audience to play the seekers and chasers, and you never know how people will behave.
"Sometimes I can see somebody there in costume, stood right up out of their seat waving their arms to volunteer, and so I think, 'they'll probably be fun'.
"But I also quite like finding someone a bit reluctant perhaps, or a little more shy, maybe their friend is putting their hand up, because I like to get a bit of a mix - somebody who's crazy excited, and someone who's a little more shy."
Though the golden snitch always gets caught, the pair are yet to see anyone actually score a goal with the quaffle. "It's great when people really go for it though," Briton laughs. "Usually you play the first round, and people are a bit timid, but then you'll get some big lad or a dad or someone going, 'I can do this', and getting out of their seat thinking 'this is my moment to shine'."
Obviously the passion for Harry Potter is very strong, and the books and films are dramatic and often rather serious, so the pair are very aware of the need to balance respect for the source material with their parody and often cheeky jibes at those serious storylines.
"Someone once said, 'oh, you must really dislike Harry Potter in order to be doing a parody of it', but I think in fact it's the opposite," explains Trainor. "I think you need to have a serious love for Harry Potter to do it properly.
"I mean sometimes fans will gasp 'how dare you!' but they also like it, and they know what we're doing, and they're playing along."
Who: Jesse Briton and Gary Trainor
What: Potted Potter
Where and when: From Wednesday October 24 to Saturday October 28 at the Bruce Mason Centre, Takapuna
-TimeOut
