It was started by reclusive local, Ant Smith โ originally with a partner โ who's still the owner.
The identity of "Ferg" remains shrouded in mystery.
In pre-Facebook days, Bradley says it was bloggers who initially spread the word.
The first celebrity endorser was supposedly Kiwi film director Sir Peter Jackson.
"There's a story he said to a couple of people, 'these are the best burgers, you've got to have them', and they happened to be Jack Black and Adrien Brody."
But Fergburger really took off when it was embraced by Lions rugby players and supporters during the 2005 tour, after it had moved to Shotover St.
Over the past 10 years, it's added the neighbouring Fergbaker, Mrs Ferg and, last year, Ferg's Bar.
While pointing out they've never hired a marketing person, Bradley says they've otherwise been a huge employer.
The empire's cumulatively employed 1860 people, including about 1150 at Fergburger, who have clocked up 2.96 million operational hours.
Beyond that, they've also been good business for suppliers of everything from beef to eggs to lettuces to T-shirts.
In return, Bradley says they've supported many causes.
"Probably our favourite is the 'gelato bikes to schools' โ we raise about $10,000 a year for schools."
Last year, they researched 17 New Zealand tourist icons and found Fergburger was No 1 for TripAdvisor and Google reviews, No 2 on Instagram and No 3 on Facebook check-ins.
They've grown with Queenstown, Bradley says โ "the queues of Fergburger have been the queues of Queenstown".
However, with borders closed, last year was probably their toughest since their first year, he suggests.
"We got through last year without losing anyone, but we're certainly now letting natural attrition take its course, and our numbers are dropping, strongly."
For the first time, Bradley admits they may consider "viable approaches" to franchise Fergburger โ till now, their back-end infrastructure has not been in place.
The company originally had bigger plans for its 20th birthday, but Bradley says the current timing is not appropriate.
"So we'll see how the 21st looks."
