It could happen in the burger queue or at a house party after a few drinks.
It's that 'light bulb' moment when you suddenly identify a gap in the market and dream up a potentially game-changing business idea.
In the UK, this moment has become known as the 'Dragon's Den' pitch - named after the popular TV program where budding entrepreneurs pitch their ideas to the 'dragons' who decide where to invest.
Many people have one of these ideas and will happily share it after a few beers. But many won't act on it because they don't have the funds - or the balls - to go for it.
For Adam Theobald, 32, the bulb flicked on in the burger queue at a Jack Johnson concert.
“After waiting for 45 minutes, some girls pushed in front of us," he says. "We reasoned with them and negotiated back to the front."
When he finally made it to the front, he ordered 25 burgers on a whim.
"I went to the people immediately behind those queue-jumping girls and sold them on at a small premium. People threw money at me," he says. "Then it clicked. People will pay for speed.”
Three years ago, Theobald ditched his investment banker job when he realised he could capitalise on impatience by creating an app for caffeine-loving workers, called Beat the Q.
You pay the same for your coffee, but don't have to wait. The app even collates your loyalty stamps for you.
One billion coffees are sold in Australia each year and his app can now be used at 230 cafés.
When I meet Theobald at his office in Sydney's trendy Surry Hills, aptly enough, I pass a long coffee queue just before I reach his door.
As we talk, he takes out his phone and uses a new prototype of his app. Just five minutes later, an employee from the nearest café walks in with my mocha and his latte.
“Soon, we won't even have to leave our seats to get our lattes,” he tells me with an excited glint and a sip.
Melbourne's Mark Middo, pictured above, had his epiphany at a backyard party.
“My best mate and I ran a small party between friends, where we all voted for our favourite retro house songs and I DJ'd the Top 50," says the 28-year-old.
"From the 50 friends there, it went viral on social media. We got random people from everywhere asking us to run a bigger event.”
Reminisce was born. It's now a night where the crowd indulges in nostalgia by choosing songs from a list of 500 provided before the event. On the night the top 50 voted songs are counted down.
The idea remained a fantasy for eight months before Middo and his best mate-turned-business partner Corey Topp, 27, made it a reality. But it wasn't all plain sailing.
“We had a few knock-backs, which made us rethink our pitch," says Middo.
The pair wanted to hold a night at Melbourne venue the Prince Bandroom, who told them that a house party was "a bit different from getting 1000 through the door".
Middo and Topp realised they needed to land a big DJ to score the venue, so contacted “king of Australian house music” John Course. Middo says they were somewhat creative with the truth.
"We cheekily told him we'd already booked Prince and all we needed was him. He signed up on the spot."
With the talent on board The Prince was sold, and their Reminisce night was held on a Friday in the middle of the 2012 St Kilda Festival.
"Putting an untried concept in place of an international act was a huge risk. If we bombed, they would've lost thousands,” says Middo.
Luckily, it was a success.
Middo has since written a book about getting a business idea off the ground quickly, The 5 Minute Business, and also licenses out the Reminisce voting system.
Two Sydney entrepreneurs, Bruce Jeffreys and Nic Lowe, dreamt up their idea - car sharing business GoGet - in a Newtown café.
“We saw cars as big lumps of metal that could be better used as a public service than something you needed to own,” says Jeffreys.
But he warns that obsessive innovation can take you too far left-of-field: “It's possible to ruin a business with too much technology.”
Is he referring to GoGet's experiment with microchips, embedded under the skin, so its customers could become life-long members? “Let's just say, so far cards have won out over embedded microchips,” is his only response to that.
But thinking outside the square has certainly worked for Jonathon Spanos, 33, who has pioneered a shoe (pictured above) for the everyday athlete that negates the need for socks, called Three Over Seven. The name represents the number of days in a week you should aim to exercise.
Made of wool, Spanos says his shoes “challenge sock industry wisdom”. But won't they get smelly, I ask?
"We like to say 'sit back and let the wool do the work'," he responds. "Our intense testing of everyday use gives you at least a month before the need to wash them.”
The quirky idea has won over the UK Trade and Industry department, with Spanos competing with 500 entrants to win one of seven places in business accelerator program Sirius. He'll soon be flown to the UK and receive mentoring, assistance in finding gaining clients, financial support and visa endorsement.
When I ask all four entrepreneurs what advice they'd give others sitting on a potentially revolutionary business idea, they all say the same thing: don't ask for permission, trust your gut and don't delay.
It's advice that could negate the need to own a car, own socks or ever stand in a queue again.