Fortunately Justin's good humour filters through into real life, and my foghorning down the phone at him does not seem to mar our interview.
"We open live shows with that and you'll hear 15,000 people joining in," he tells me, (translated: I've heard it all before.)
My audience with Justin is granted to chat about his new project, voicing 'Olly The Little White Van' who rip roars his way onto CITV from June 26th.
Justin is as affable and excitable in real life as he is on the TV. His passion and enthusiasm is palpable, his drive and professionalism steely. He successfully manages to keep my questions well and truly on track - answering everything put to him fully, yet without giving too much of himself away.
I sense Justin has a work on/off switch, and he has clear boundaries between the two. I wondered though, how a now 41-year-old man from Reading ends up becoming probably the most well loved and well known kids' entertainer in the country? Or, what kind of chat do you have with your careers teacher that ends up with you becoming Mr Tumble?
"I was always really interested in kids' TV when I was at drama school," Justin explains, "And in the third year I got to go and see Phillip Schofield and Gordon the Gopher – I thought I could have a go at that kind of entertaining, and I got my sister to make me a show-reel. She was a newsreader at Meridian, and I just came up with a couple of characters, did a piece to camera and she put it together for me."
Justin landed work just weeks later, firstly for CITV's Fun Song Factory, then later with the BBC, touring as Mr Jolly in Playdays, and then on Tikkabilla, where he was working when the idea for Something Special came along.
"Something Special was initially a pilot with very little money behind it," he says, "I was told it was going to help children with learning difficulties and that I would need to learn Makaton sign language. I went on a crash court – I had a week and a half to learn 400 signs – and the programme just exploded overnight."
But learning 400 signs in a week is surely nothing for the man who never seems to be off the box – as I reel off the list I have of all his TV credits, voice-overs and characters, he laughs and agrees he does work a lot:
"I do work too much! I am planning next year to have a few days off. But yes, I work very hard and love what I do, and the feedback I get drives me and keeps me going. Often people use this kind of work as a stepping-stone to daytime TV or whatever, but I love it."
Justin reminds me that he is trained as an actor, and that drama or adult comedy is something he would like to explore in the future:
"I have been approached by couple of production companies to do various bits and pieces, and would love to explore that, but things are so busy at the moment. I would love to do adult comedy though. Actually, Peter Kay and Simon Pegg contacted me recently - they have little children – and Peter Kay sent me a lovely email about Gigglebiz. So yes, some adult comedy would be great fun!"
I wonder if Justin realises the cult following some of this programmes have, how Gigglebiz has been described as 'Little Britain for children', and how students miss lectures to watch the shows.
"Pre-school Little Britain! Yes! And Gigglebiz does have a huge student following. You know you are making an impact when someone shouts out one of your catchphrases to you! I went to a campus a little while ago and lots of the kids were wearing T-shirts with my characters on. And at the Bestival festival there were loads of older teenagers dressed up, too."
So where do all these characters come from? "I watched people's mannerisms." he says, "I base characters on people, tweak them a bit, make other little notes about them. I always carry a hard disk recorder and if I hear an interesting voice I put a demo down. Really helps, especially as I have done a couple of hundred characters in 15 years. I need to keep all the mannerisms and vocals different. I find that a challenge. So I write everything down too. I am doing seven or eight voices in Olly, and there are 26 characters in Gigglebiz, so I need to keep track."
I wonder if anything ever fazes Justin – if he ever gets embarrassed?
"Not at the moment! In the live shows you run out on stage in front of thousands of kids and they just love it – there's no room for embarrassment. I was always taught the three Cs of children's entertaining – clarity, contact, commitment. If the kids believe in you, and you engage them, then you're there."
But SURELY there must be some jobs that are just plain weird – after all, not many men go off to work each day and find themselves donning a bonnet and sitting in a pram, or gurning to camera for an eight hour shift?
"Well, there was one funny job – not odd, because I loved doing it, but when I was voicing Shaun the Sheep the casting was very funny. All those baas. Trying to get a message across in sheep baas! Oh I did many years of training for that! A lot of working on the farms. Actually, I didn't, I just went in all guns firing, did a high energy performance with a bit of prep and played around with some voices. Like I do for all my characters."
Being Justin Fletcher must be something of a bind though – distinctive even out of costume, surely he can't get a minute's peace? Are people always fostering their offspring onto him at parties and chasing him down the street for autographs?
"Er, yes. And I get a couple of hundred emails a week asking me to lots of parties, and to open school fetes and things. Lots of charity requests. They are very important."
Amongst his charitable endeavors, Justin is a patron of the Make a Wish Foundation, and it was partly for his charity work that he was made an MBE in the 2008 birthday honours.
It's just all so lovely and squeaky clean that I can't help but ask him, as we round off our interview, is it HARD being 'Justin Fletcher from Children's Television' and constantly having to preserve that squeaky clean image? Does it rule out kicking back at the weekend and getting rip-roaringly drunk down the local? Justin is very careful not to entertain my frivolous questions with an in-depth answer, preferring to neatly swerve the issues with a swift:
"I think it comes down to common sense!"
But, he continues, "I do get good good feedback. If I'm in the supermarket I'll happily sing and do autographs and pictures. You get children see you and bump into something because they are transfixed. Last week little girl shouted "I never thought you were part of our world!"
You're def part of our world, Justin! check out a clip of Justin's new show, Olly the Little White Van.