No one predicted the release and subsequent viral sharing in early September of oddball music video “What does the fox say?” by Norwegian duo Ylvis, which today has attracted more than 151 million views on YouTube. Web-only costumes seller HalloweenCostumes.com, though, acted quickly to make the most of the phenomenon.  The video’s popularity helped it to sell more than just costumes of foxes, but also the parts for customers to create their own fox costumes, says vice president of marketing Mark Bietz.

In fact, selling parts for self-made costumes helped the retailer to satisfy more customers  after demand resulting from the viral video caused it sell out of some costumes, he adds. “The demand for fox costumes was really high—any year before, we never had issues with keeping fox costumes in stock,” he says. “We have to get pretty creative, but typically we do have enough accessories and costumes that would fit the bill with small alterations by the customer.”

After selling out of one fox costume within a week or two of the video’s release, a member of Bietz’s staff blogged about how customers could use various items from the retailer’s catalog—including ears and tails, a masquerade mask and face paint—to recreate the look of the lead fox and the fox dancers from the video, Bietz says. The post quickly became one of the most popular on HalloweenCostumes.com’s blog, he says, and it showed up in organic search results. As a result of adding do-it-yourself and other costume-related content to the site, he says the retailer’s blog traffic has been up 200% year over year and revenue is up 300% year over year.

“There are definitely surprises that happen every year, especially with things that aren’t a big movie or traditional Halloween costume,” he says. For example, last year after former presidential candidate Mitt Romney said he’d end funding for public television and the popular Sesame Street character Big Bird, the retailer blogged about it and mentioned its Big Bird costumes, which customers rushed to buy, Bietz says.  

“Typically when something big like that happens we put up a blog post about it and our marketing team tries to get it posted on many web sites and media outlets to let people know we have it,” he says. “We don’t really have to up our efforts on paid search. When something catches fire like that it happens organically.”

Although 80% of HalloweenCostumes.com’s revenue comes in September and October, the retailer also sells a fair amount of turkey and pilgrim costumes around Thanksgiving, and Santa Claus and elf costumes around Christmas, too, he says. The retailer’s main marketing strategy in preparing for those holidays, and for the foreseeable Halloween sales, is to bid aggressively on many specific paid search keywords and phrases, he says. It also advertises on comparison shopping engines.

This year, the retailer began advertising with Facebook’s new retargeting tools—which have increased traffic from the social network by 40% year over year—and upping its advertising on YouTube, Bietz says. Across all those marketing outlets, HalloweenCostumes.com beefs up its spending by about 10 times during the September-October period, he says.