However, the theatrical eye hair of the all-round entertainer is perfectly apposite because his regular countenance is one of astonishment. Clarke can't quite believe at 32 he's already flirted with Britney, currently presents the breakfast show on Capital FM, has won a clutch of prizes for his stand-up and is currently more in demand on the after-dinner circuit than Abbey Clancey is for twirling in sparkly frocks.
He still can't quite get his head round that it's not so long ago his daydreaming head was facing out of the window of his family's 21st floor Gorbals high-rise looking at the Citizens' Theatre and assuming that's the closest he'd ever come to showbiz.
"I was really quiet as a kid, with specs and face spots, he says, in a quiet corner of the King's. "My dad is a manual labourer who does paving work and I certainly never went to stage school."
Yet, when shy little Des stepped up to big school, Holyrood High on the south side of Glasgow, his confidence grew dramatically. Somehow, "like in a scene from Quantum Leap", another confident, showbizzy extroverty young man had leapt into his body.
"I don't want to say I've always had voices in my head, but I suppose they were there in primary, when I'd think about impersonating teachers. And I guess in going to high school, and attending drama class, the voices emerged and the part of me which had always wanted to grab the limelight won out.
"Before I knew it, I was writing sketches and up there on stage in the First Year School Talent competition and impersonating Chris Eubank, Billy Connolly and the teachers. Suddenly, I was getting encouragement, and laughs."
He adds: "I've never taken drugs, but I'm sure the feeling you get from applause is all the more powerful."
During school years, Clarke became the go-to guy for speeches, shows, renditions; he was clearly a stick-on for a career in entertainment.
"I had a wee thought about acting when someone from the RSAMD came to our school careers open day. This bloke asked me if I could sing and when I said 'No', he said I'd be wasting my time applying." He adds, with a wry grin; "It's ironic I'm now leading the song sheet at the King's panto."
Aged 17, Clarke still never believed he could be an entertainer and with a clutch of Highers took himself off to Glasgow University to study Film and Television. But one night the call of the comedy wild - an open mic spot at Glasgow Blackfriars - became too strong.
Studies were on hold for a year while he pursued the dream. After he came second in So You Think You're Funny at the Edinburgh Festival in 2000, the studies were put on hold for ever.
"I was up against the likes of Matt Horne and Russell Brand," he recalls. "Russell was battling with his demons at the time. He walked on, ranted for ten minutes and stormed off. And I thought, 'We've seen the last of you, mate.' Shows what I know."
Clarke soon landed the chance to develop his voice on radio, working on Beat 106 alongside Heather Suttie and he went on to win a national broadcasting award. Inevitably perhaps, television came calling and the impish, infectious hi-energy Scot was signed to replace Ant and Dec on SM:TV, partnered with Tess Daly, Cat Deeley and Brian Dowling.
"I was 22 and suddenly I was doing live telly on a Saturday morning. And I couldn't believe it. I had since moved on to Capital Radio, was recording my morning show from the London studios, then being picked up by a motorbike to be raced to the SM:TV studios to interview Robbie Williams, Kylie or Madonna, who glided in to the studio as though she were on a hoverboard."
Clarke came up with a character, Eminemmerdale, based on the life of the rapper set in a soap. And his character went down a storm, which is more than can be said for the fake door he was supposed to crash through when interviewing Britney Spears.
"It was meant to be made of foam," he says, his serious voice recalling the pain of the moment. "But it was solid. As I burst through this door, dressed in rapper gear, I ripped my hand (he reveals the decent-sized scar) and the blood burst out.
However, no one had told Britney's boucers, two giant black guys, who were off stage watching her, that this Glaswegian nutter would be surprising her. And so they ran into shot to take out this stalker. Me. Luckily, a producer got to them before they got to me."
Life was all too surreal for the good-looking, charismatic young Scot. "I had the gift of the gab and the cheek," he says, grinning. "I'd be talking to Britney or the likes of actress Jennifer Ellison and think, 'I'm in here!' And I remember Kerry Katona getting particularly friendly, although I backed off there. I also reckoned there was a bit of chemistry with me and Holly Valance as well. And I thought I could have pulled at least one of the Sugababes, given there was so many of them, their line-up changing so much." He adds, laughing; "I could have been a Sugababe at one time.
"But the truth is I never got a single phone number. It's only later on you realise you had a 'chemistry' because they were trying to sell their new album."
After spending Saturday mornings in Babeland, Clarke, who now has a regular girlfriend, Deborah, would fly back to Glasgow - and down to earth.
"I'd sit at home on a Saturday night with a cup of Bovril and think 'What just happened there?'"
What happened was he was growing up, coming to realise showbiz casts bright lights - and even brighter shadows. And he matured as a performer, going on to attract the attention of panto bosses.
Last year, Clarke picked up great reviews for his Buttons at the King's. However, he's never allowed himself a moment to think he's arrived. "I don't drive, so I didn't buy a flash car. I've never had an entourage, except for the two guys with ginger hair I'd gone about with since school.
"It's not that I didn't enjoy all the telly attention, I did. But the working class thing always kicked in with me. I always thought 'Should I be here at all?' And then I'd reckon it could all go in a minute, so I didn't want to blow it by doing anything daft."
He adds, in serious voice; "I still feel that way."
It's perhaps that belief which has propelled his career, making Clarke believe he has to continually up his game. And he does. And the result is he leaves audiences in stitches.
And speaking of stitches, three weeks ago, while in full Wishee Washee flow, a piece of heavy wooden scenery collapsed and fell on his shin, leading Clarke to later Tweet a picture of his panto injury.
"I was still in panto mode so I couldn't use the swear word I wanted to let out," he says, grinning. "So I screamed 'Flip!' and ran off stage. The next scene involved me dancing, and in tights, which are a bit uncomfortable for a man with a particularly hairy leg, but now they were causing me complete agony. Yet, it's the old showbiz cliche. The show must go on. So the blood was mopped up and on I went, limping on one leg."
When he was a kid could he ever have imagined standing on the King's Theatre stage in blue silk blouson trying to prevent an audience of weans from seeing blood seep through white tights?
"Not a chance," he says, grinning, before his voice drops to a more reflective tone.
"What was great about getting the King's panto was the endorsement. I need to be told I'm good. I need to hear the crowd's applause. I think I'm good, but I don't necessarily always believe it, perhaps because I can't quite believe what I'm doing."
He rises to a laugh again, perhaps realising how serious he has been sounding.
"My mother has been to see the panto four times already. She can't quite believe it either."
He adds, of the panto experience, but perhaps referring to his showbiz life; "This is special. Really special. And I never forget for a minute I'm walking in Gerard Kelly's shoes. I'll take a leg battering anytime to do this."