Quite what that would entail is anyone's guess. It's difficult to imagine him in anything other than his trademark suit, giant-collared shirt and black rimmed spectacles.
I try to picture him in well-pressed chinos and a crisp blazer. Perhaps a Juicy Couture velour tracksuit with diamante-encrusted rear. The door swings open to reveal the comedian looking, well, exactly as he does if you were to do a Google image search for the words "Harry Hill" - right down to the chunky gold jewellery, brothel creepers and neat row of pens in his top pocket.
He peers owlishly from behind glasses as thick as jam jars, a thatch of dark chest hair protruding from the unbuttoned neck of his shirt like a Tom Jones impersonator, incongruous against the cue ball baldness of his head.
Ever since Harry Hill's TV Burp departed to the great big telly heaven in the sky last year, it has left a gaping chasm: there's nobody to point out the many faces of Louis Walsh (surprise, joy, smug, outrage, sad and Hitler), spread word of Val from Emmerdale's deteriorating eye problems (Cataracts? Cataracts?) or reveal the true father of Heather from EastEnders' baby (Mr Blobby).
Saturday tea-time hasn't been quite the same without an eagle-eyed Hill to spot the uncanny resemblance of Viennettas on a factory belt to "German tanks rolling into Poland" or taking the mickey out of Russ Abbott's not-so-star turn as a heart attack victim on Casualty. Who can forget an emotional Hugh Fearnley-Whittingstall surveying a barn packed with 3000 hens and imploring: "What animal of any kind would like to live in here?" before the camera panned back to Hill, who quipped: "A fox."
The 49-year-old returns this week with an eponymous film, tipped as this year's big family Christmas movie. As one might expect it is left-field, offbeat, kooky and all manner of other similar adjectives you might use to describe a plotline in which a middle-aged man and his nan go on a road trip to Blackpool after discovering his hamster only has days to live.
Throw in chickens with machine guns, garden gnomes, Ibiza-style partying, pillow fights, a car wash, evil twins, mobility scooters and a projectile vomiting rodent and you're halfway to picturing the plot of The Harry Hill Movie, which he describes as "a bit like Pee-wee Herman, but me on my adventure".
It's an intriguing insight into the workings of Hill's mind. "I had this idea of a B&B being run by the band The Magic Numbers - partly because I like their look," he says. "There is a car wash song when we go to get petrol with Shingai [Shoniwa] from Noisettes. Then there's this silly story of the hamster that holds it all together."
The cast includes fellow comedian Matt Lucas, Gavin & Stacey actor Sheridan Smith, Simon Bird from The Inbetweeners and national treasure Julie Walters. Hill breaks into a grin. "She is so playful and like a little girl," he says. "When they said we'd try to get Julie Walters, I said: 'There's no way she'll do it, you're joking,' but luckily she did.
"Once we got her on board it made everyone else want to do it. It also made it like a proper film because she is a proper film actress. I didn't want people to think it was like a long episode of a TV show."
With a fan base stretching from "ages seven to 90", Hill was equally keen to make sure it had family appeal. "What we tried to do with it is a bit like those Pixar movies where it's great for kids, but there are a lot of laughs for parents that will go over the children's heads," he says. "It's like when you go to a panto, the idea is it works on two layers. I took my kids to see the Smurfs film, which was really painful. They loved it, but I didn't get anything out of it."
He and his wife Magda Archer have three children - Kitty, 16, 15-year-old Winnie and Freddie, nine. While the nation mourned the loss of TV Burp, it was all his two eldest could do not to break into a conga. "They hate me being on television," he admits. "Freddie is looking forward to seeing the film as she's the right kage group, but the other two, when I said to them I was giving up TV Burp, they cheered: 'Yeah!' They asked: 'What are you going to do with all those big collared shirts?' I replied: 'I still have to do that - where do you think we get the money to go on holiday?'"
Hill shakes his head when asked if he himself misses doing the show. "I don't, actually," he smiles. "It was always a slog. I don't miss it at all. Recently I have started watching television again and enjoying it. I watched a documentary about hairstyles the other night on BBC Four and it was the first time I'd sat down and been a punter.
"Although, that said, I was watching Ben Fogle's Animal Clinic recently and thought: 'If TV Burp was still on we'd get about 10 minutes out of this.' It was about a big fat dog. I can't help myself from spotting things."
The second of five children, Hill - real name Matthew Hall - grew up in Staplehurst, Kent, where his own childhood television favourites included Tim Brooke-Taylor, Graeme Garden and Bill Oddie. "With TV Burp I used to get a lot of letters from nine-year-old boys and when I was that age I used to love The Goodies," he recalls. "I suppose it's a similar thing."
Some two decades have passed since Hill packed in a budding medical career to pursue comedy. "I'm proud of having given up being a doctor because it was a big decision to make," he says. "Looking back, I'm surprised I did it. That was the big moment."
He first pricked the public consciousness in 1993 when commissioned by Radio 4 for a series called Harry Hill's Fruit Corner. His television debut came a year later with Fruit Fancies on BBC Two, followed by his own Channel 4 sketch series, Harry Hill, in 1997, where quirky oddities such as "The Badger Parade" would help stoke his burgeoning cult status.
In 2001 ITV signed him up for Harry Hill's TV Burp, which ran for 11 years before he decided to call time on it. He believes the team "quit while we were ahead".
"My worry was if we'd kept doing it, it would start to get ropey," he says. "I was losing interest in it a bit and I think when that happens, the last thing you want is for the quality to slip.
"It was always on a knife edge because we would start at the beginning of the week with no show and need to have one by the end. So it was always, in my mind, a panic. At times I didn't sleep at all. It was an enormous amount of television. I'd watch 10 hours a day up to about 40 hours a week."
It had been his hope to pass the baton on but admits: "I couldn't get anyone else to do it." He gives a small shrug. "I tried a number of comedians but none of them could be bothered."
Hill hasn't been idle in the months since he hung up his TV Burp cap. In addition to making The Harry Hill Movie - which is still undergoing the rigours of post-production when we meet - he has continued to lend his dulcet tones to the voiceover of You've Been Framed, providing witty one-liners to accompany assorted trampoline mishaps, dropped birthday cakes and toppling babies.
He helped mastermind a spoof remake of A-ha's Take On Me video for BBC Children in Need in November and since the start of the year has been immersed in another pet project, I Can't Sing! The X Factor Musical, which is set to open at the London Palladium next summer. The latter is a tongue-firmly-in-cheek parody of the television talent competition format and has won the approval of music industry svengali Simon Cowell.
Hill grows animated when it's mentioned. His love of The X Factor, he says, stems back to documenting it in his TV Burp days and in 2011 came a lightbulb moment. "I was watching the final - drunk - and had this idea," says Hill. "I mean, I have a lot of ideas, but most of the time I don't pursue them. I called Steve Brown, who wrote all of the music for TV Burp and has written musicals in the past, and persuaded him to meet and talk about it. Once I got him on board, I then had to get Simon Cowell on board."
How difficult was that? "It was really easy," he grins. "As it turned out they were thinking along the same lines. We had a first meeting and they asked us to come up with a storyline. It all came to a head in January last year when we had this sing through workshop which Simon came along to. It was basically going to be yes or no - a bit like The X Factor - and we were all really nervous," he chuckles.
Did Cowell do that serious face where he pretends it's bad news, pauses for a beat, then announces they are through? "No, he was so excited he couldn't contain it," says Hill. "It was really touching and we were all thrilled. I can't wait until it opens."
Hill insists it is "gentle and flattering" when it comes to poking fun at Cowell. "We aren't being nasty in an aggressive way, more over-praising him," he says. "We are making out like he's Jesus, healing the sick and almost like he has special powers. The musical isn't really about him, though. He's not in the first half much, as that's when we follow the hopefuls and weirdos."
In that vein, Hill promises the "back story to end all back stories" - a hunchback. "He was brought up by hedgehogs and the only time he feels free is when he can sing," he says. "But they [the judges] tell him he hasn't got the full package - he is the king of those 'types'.
"What we had to do is avoid all of those jokes that have already been done about The X Factor. The nastier side of it is when the hunchback gets rejected and does this Eminem rap where he absolutely lays into the whole X Factor thing.
"I was thinking: 'Uh-oh,' as it does say everything that the people who hate the show - and I'm not one of them - feel about The X Factor, such as it's exploiting people and so on. It's chilling, fantastic and funny."
Has Cowell invited him on to his yacht? Hill looks across with one of those perfectly timed sideways glances. "Not yet - but it can only be a matter of time," he deadpans. With Nigel Harman lined up to play the music mogul in The X Factor stage production, who would play Hill in the musical of his life? "Al Murray, perhaps? But I don't know if he's available."
As much as he adores The X Factor, Hill is less keen on the foxtrotting, cha-cha-ing sequin-bedecked celebrities over on BBC One. "I never got into Strictly," he says. "I'm a big fan of Bruce Forsyth, but I don't have any interest in people learning a new skill that's not going to be of any use to them in the future. It's a bit of a turn-off - a bit BBC. There is a slight tameness about it. It's just a taste thing, I'm sure. I think you either fall into one camp or the other."
What would it take to persuade him to go on Strictly Come Dancing? "A lot," he says. "I can't be bothered. For me, it's always about: why do you want to be on TV? If it's something that really interests me then it's worth sticking your head above the parapet. There are good and bad things that come out of being well known and you need to make sure you are doing something you really like.
"I don't want to be on TV for the sake of it. If I wanted to learn how to dance then I'd take lessons. I once got asked to do celebrity show jumping. It involved three months of learning to ride a horse then you got on the show. I mean, who's got the time?"
While his wife is a respected artist, Hill enjoys dabbling as a hobby. "I had an exhibition when I was at the Edinburgh Festival last summer which was good fun but I don't sell them really," he says. "Well, I did sell two. They were in the Royal Academy's Summer Exhibition [in London] and you have to put a price on them. I didn't really want to sell them so I put a really high price on them. One was £3000 because I really liked it and the other was £1500 - and they both sold. One was of a horse on a surfboard and the other a formula for muck."
A few years ago he went through a phase of turning pages from Hello! magazine into oil-painted works of art. He's moved on from that and currently dabbles in large-scale pieces. "I'm working on one at the moment which is made up of six panels," he says. Hill jumps up and spreads his arms along a nearby wall like a fisherman exaggerating his catch. "It's about that long. My idea is to keep on making more and more panels. I have no idea where it's going to go. It's a bit like a modern-day Bayeux Tapestry."
I remain curious as to what he wears off-duty. "A onesie," he jokes. An image of a giant baby floats before my eyes. "I just wear normal clothes," he continues. "I might wear a suit. I wear a whole spectrum of different clothes. I don't wear this, if that's what you are getting at." Which, in a way, is strangely disappointing. n
The Harry Hill Movie (PG) is in cinemas from Friday.