Wispa, an aerated chocolate bar distributed by Cadbury in the United Kingdom, has been getting a lot of new fans, as we noted yesterday. Looking closer, the reason appears to bode well for a dedicated group of people who love a type of Wispa bar called “Gold” because of its extra caramel.

The Gold, along with the rest of the Wispa brand, was removed from distribution in 2003 as part of a company effort to streamline its product lines. A Facebook-fueled campaign in 2007 convinced the company to bring back the original Wispa bar, first as a limited edition. It did so well that the company made it permanent — and is now trying to see how the Gold does on the market. A group of Gold devotees, only 22,000 strong, convinced the company to re-introduce it earlier this year.

The Gold was just launched on September 8th, and since then the page has grown from a flat-lining 266,000 fans to nearly 500,000 today. It’s not clear what’s causing the growth. Cadbury has a contest for Gold, where you can compete to write a message that will appear on billboards near where a loved one lives in the country. But the contest is run off of Cadbury’s home site, and doesn’t appear to even mention Facebook.

One possibility: The hardcore group of Gold lovers is the visible fraction of a far larger nugget of fans, people who are showing up now that the bar is out on shelves. Although these fans don’t seem to know about the actual Wispa Gold page, which is basically nonexistent. If the Wispa page keeps growing like this — and if it’s growing because of Gold’s reintroduction — Cadbury might want to make this version of the Wispa bar permanent as well.