It's been almost 40 years since Dr Karl Kruszelnicki first started talking science on the ABC's Triple J, or Double J as it was known then.

Over the decades, Dr Karl has become a regular on our TVs, published a library of books and been awarded prestigious honours including an Order of Australia and the UNESCO Kalinga Prize for the Popularisation of Science.

To many of his fans, Dr Karl is as famous for his knowledge of all things science as he is for his eye-popping shirts.

His wife Dr Mary Dobbie is behind the iconic vibrant threads.

"It's basically 99.99% Mary, and I'm just the grateful acceptor," Dr Karl told the Mix.

"You're the beautiful body, the display horse," Mary replied.

"Lots of people won't wear what I make for them, so I'm lucky that Karl will actually put the shirts on and wear them out the door," she said.

"It was a way for me to justify buying material and have something to do with them."

Men's fashion was too plain

Mary and Karl met in first-year medicine at the University of Sydney in 1981.

"He was really conspicuous, he sat right at the front of the room and would stand up and tell people not to throw paper airplanes," remembers Mary.

"So he was always obvious."

It was during her early 20s that Mary began to make shirts for Karl, who wanted colourful clothing to wear to work.

"He's definitely there for maximum impact and men's shirts just didn't really cater for that," Mary said.

Karl had a vibrant vision for how he wanted to dress.

"There is a philosophical set that is: 'I will dress with one colour of the rainbow and various shades,'" Dr Karl told The Mix.

"Whereas mine is: 'I will dress in every colour of the rainbow all at once.'"

While Dr Karl doesn't mind what material Mary chooses, he does have specific requirements that the shirts have two pockets and a line of stitching to hold a pen.

Full-length sleeves are also an essential design feature, but not for wearing long.

"I'll walk onto stage and the sleeves are rolled down and buttoned up," Dr Karl explained.

"While talking to the audience, I roll up the sleeves and they'll get the background message that we're getting to business now."

The satisfaction of sewing

Mary works as a clinician with a sexual assault service in Sydney.

Sewing is a hobby that balances out the intensity and open-ended nature of her work.

"People come in then go away, I never see them down the track and you hope you've done a good job," Mary said.

"If I sew a finished product, something I can see and touch, that's really nice to see something all the way through."

Mary is aware that working with sexual assault victims can make her prone to developing vicarious trauma — an affliction caused by reading, hearing or seeing harm caused to other people.

"That's how I stay out of that headspace, by having things that are completely separate and unrelated," she said.

The creations are a team effort, of sorts.

"If Mary is like, 'Let's go have a look at this fabric shop', I'm right there," Dr Karl said.

"It's none of this, 'I want to sit down and play on my PlayStation' sort of business."

There is some trade off.

"In return, I go to Jaycar endlessly, that's the deal," Mary added.

Why wouldn't you wear bright colours?

Dr Karl's fashion philosophy comes from his appreciation for the visible light spectrum … the range of colours that the human eye can see.

"We do have friends who specialise in wearing various shades of grey on grey," Dr Karl said.

"We have the ability to see a rich palette of colours so why not enjoy it to the maximum?"

Dr Karl regularly gets approached by fans wanting a shirt made by Mary.

"It's an act of love rather than a commercial entity," he told The Mix.

"You could get them made really cheaply but then there's a whole lot of emotional baggage and exploitation associated with that," he said.

Like with a lot of bold fashion statements, it has its critics.

"I think you were once voted the worst dressed on some list of worst dressed," Mary laughed.

"I can't remember who they were but they were wrong, you were right," Dr Karl said.