But it's hard not to think he should be wearing a Fifties suit and his hair Brylcreemed.
The comedy entertainer, who stars as the Tin Man in The Wizard of Never Woz, is just 33. But he's an unusual showbiz creature in these times.
Johnny is an old-style variety entertainer, an all-rounder who can tell gags, do impressions, perform sketches and act.
Were we living in the Fifties or Sixties, there's little doubt Johnny would be sharing a stage with the likes of Lex McLean or Jimmy Logan.
"I guess I would be," he says, smiling.
"There are still variety style entertainers around today however, like Lee Evans and Michael McIntyre.
"But I also grew up with a real awareness of Francie and Josie.
"I'd watch their appearance at the Garden Festival. And I'm a big fan of Billy Pierce and Brian Conley. And Freddie Starr, in his younger days."
John MacDonald grew up in Kilmarnock and was the typical class clown, the kid who entertain the pupils and teachers.
His parents recognised young John was born with the natural show-off gene and packed him off to youth theatre – and he loved every moment of it.
At the age of 16, he was running his own discos and kids' parties and when he left school Johnny became Johnny Mac, and took off to the sun to become a holiday Red Coat.
There was never any doubt Johnny wanted to become an entertainer.
"I don't think there's any better feeling," he says.
"And when you appear in a panto such as this, with 1200 people watching you, it's quite incredible."
Johnny has appeared in pantos across the country. But most of his work is variety-based.
"I work in the summer seasons which have survived," he says talking of resorts such as Bournemouth and Great Yarmouth.
"And I manage to get around 10-12 weeks each year."
He also takes his act around the cruise ships.
"It's great, to be flown out to a ship in a lovely location and be treated well and do one or two nights," he says.
Johnny, who now lives in Glasgow, has suffered a little ignominy along the way. He recalls one particularly tough appearance as a raw, and vulnerable, 22 year-old stand-up.
He says: "I played a club once, Saughton Prison Officers' Club in Edinburgh. When the social convener took to the stage to introduce me, all he said was 'It's a Race Night, ladies and gentlemen.
"And everything tonight in the club is free. Except for the act that's coming on.'
"He never even mentioned my name. As a result, I came on and did 20 minutes and never got a single laugh. And the atmosphere got worse.
"Then the social convener, who was sitting at the back of the hall called out 'Right, son. That's you. Get off!' And I did."
But the embarrassment wasn't over.
"I had to pick up my speakers and amp and carry them out right through the middle of the hall," he said.
"It was like something out of Phoenix Nights.
"Yet, people don't really go to clubs to see the performer. You have to convince them you're worth listening to. And that's what I try to do."
He adds, smiling; "Someone once said to me 'If you die on stage and wake up the next morning and still want to entertain, you know you're in the right business'."
l The Wizard of Never Woz, The Pavilion, until January 19.