"It's been unbelievable," Clarkson told United Press International in a recent phone interview.
"When we were in the United Kingdom, when we first went to the West End, there was the fear, 'Will everyone get this?' And then when we went to Toronto, I remember that fear came back and then when we came to New York, there was the fear that they were just going to look at us and say, 'Who are these two British guys on stage and what are they doing?' So, it's been overwhelming," Clarkson explained. "The audiences, the way people react in New York is brilliant. Just the urge to shout out and if they want to say something, to just go for it, and the applause and the cheering. In Britain, we're very polite and very reserved, so this is amazing."
Preview performances of "Potted Potter" began in May at Manhattan's Little Shubert Theater and it officially opened June 3. This is the production's U.S. premiere after successful runs in Toronto, London, Edinburgh, Australia and New Zealand.
It's limited engagement in New York was initially to end next month, but was extended through Sept. 2, due to popular demand.
In the show, Clarkson and Turner use sparse sets and silly props, as well as the imaginations and good will of audience members, to enthusiastically conjure up in little more than an hour the magic of the popular book and film franchises about a boy wizard named Harry.
Asked if they think their show is so successful because the humor is universal, the actors are quick to give credit to the source material.
"It's been translated, I think, into 71 languages worldwide, second best to the Bible," noted Turner. "And I think we've been very lucky that our humor seems to have translated over here, as well, because there's no guarantee. Some things come through very well -- Monty Python [from England] and 'Saturday Night Live' the other way -- but for every success, there's a failure. We never quite know if our British humor is going to roll with you savvy New Yorkers."
"The only things we've changed are the pop-culture references because, obviously, some of them are different back home for us. But the humor, the jokes themselves, pretty much remain the same," Clarkson added.
One way he and Turner keep having fun with the show is to bring members of the audience -- who can be unpredictable -- up on stage.
"Part of the show for us is the improvisation element. With something like where we playing the game of Quidditch, just the joy of not knowing what's going to happen really keeps the show fresh for us because when you get two kids up on stage, you can't script two kids," Clarkson said. "If something comes into their head, they're just going to say it and you're going to roll with it. Where we would think A to B to C, they think G to H to I and eventually get back to C and it's amazing to be on that journey with them, going, 'This could go anywhere.' And loving every minute of that."
"It's funny that Dan described it that way because that's what it's like sharing the stage with him, as well," Turner joked.
The actors said they hope the ordinary props and low-tech nature of the show encourages young audience members to use what they have around the house to bring the characters from the Harry Potter books to life on their own.
"Children who are watching the show, they could go home and with their own dressing-up box, kind of re-create what we did and it's rather exciting their imagination and so, instead of coming out in full Ron Weasley Gryffindor gear, going, 'Well, with just this wig, I can be Ron Weasley.' ... It transforms the imagination, so the audience almost kind of fills in the blanks for us."
"And also I think if it was full costume with all the running around Dan does, he'd have a heart attack halfway through Book 4," Turner laughed.
"I get a great workout every day," Clarkson admitted.
"We are very much fans of Potter and so we don't in any way want to appear as though we are degrading Potter or being derogatory towards it, but the real problem for us is the fans because the Harry Potter fans -- there is nothing like them in the whole world! You get anything wrong and they will shout out," Clarkson said.
"Everything we do on the stage comes out of love for the series. We love them first and foremost and if we didn't and that didn't come across, the fans would have made sure we stopped the show a long time ago. The Internet is a powerful tool," Turner emphasized.
Clarkson recalled how Radcliffe considered, then thought better of attending a performance of "Potted Potter" when he was in the West End starring in "Equus" several years ago.
"At that time, we were playing a 200-seater and the thought of him sitting in the middle of a venue with 200 seats, surrounded by Harry Potter fans, we sort of decided he'd never get out alive," Clarkson remembered. "So, we promised him we'd make a kind of diving cage they use for sharks, if he ever comes to see it."