Unbeknown to most of them, about 350,000 Aussies have actually driven an Opel.
But the ignorance is understandable.
The Opel's lightning-bolt badge had been removed and replaced with a Holden lion, sometimes with a bit of locally designed cosmetic change.
Of the Holden Astras sold in Australia, most (an estimated 250,000) were actually Opel Astras.
Holden stopped imports of the Astra in 2008, despite the vehicle being widely loved. Even now, Roy Morgan Research says Astra is the third-most-recognised small car model name in Australia.
The Holden Barina - a flirt if there ever was one - has a far more complicated backstory.
While carrying the Holden Barina badge for more than a quarter of a century, the real identity of the car hasn't stayed so true. About 100,000 Barinas have been Opel Corsas while others have been cars engineered by the likes of Suzuki, Chevrolet and the Korean-based GM-Daewoo.
The Opel Corsa version of the Barina, a Wheels car of the year, was dropped by Holden in 2006 because it couldn't compete on price with Korean cars such as the Hyundai Getz.
The Holden Barina badge was then planted on to a far inferior GM-Daewoo Kalos.
Initially, this Barina had an abysmal two-star crash rating, not a good look for a Holden being marketed at very inexperienced drivers.
The 2011-12 Holden Barina, also from Korea, is a vast improvement and has a five-star crash rating.
Another Opel we've had, but with a lion badge, is the Vectra.
That midsize car ended its run in 2003, when Opel launched the Insignia, a light-years-better car.
But, with Aussie-dollar/euro exchange rates nowhere near as favourable as today's, Holden passed on the Insignia.
Four years later, Holden resumed play in the midsize arena with the Epica, a GM-Daewoo offering.
It was as chutzpah challenged as a Toyota Avalon, and died a quiet death in Australia in 2011.
These days, there's no slagging off at Korea. Just look at the excellence of Hyundai and Kia.
And GM-Daewoo's Cruze (now built for our market in Australia) and Barina are good buys.
The smaller Opels - Corsa and Astra - are a more premium, high-tech offering than the Holden Barina and Cruze. For that, there's a small price penalty and a much sparser dealer network.
Though, when matching the cars' performance, fuel economy and specs, there's arguably little or no price difference.
The Insignia, a classy piece of kit to consider if looking at a Volkswagen Passat or Honda Accord Euro, will also play against a very interesting "Holden" entrant.
It's next year's Holden Malibu, which is really a Chevrolet Malibu from the US.
The arrival of Opel gives Australians access to arguably the best of GM's global cars - those from Europe.
Yet we'll also be able to buy interesting GM cars from the US and good-value ones from the rapidly improving Korea.
Consumers will be spoilt for GM choices, which I think is a nice thing.
The other Opel we've had, but with a lion badge, is the Vectra. That ended its run in 2003.