WASHINGTON ( TheStreet) -- Yes, it's Halloween shopping season, but most pop-up stores opening in October won't have that sexy nurse costume you're looking for.While holiday outlets and costume shops will continue to fill in Main Street's whitewashed windows and vacant stores, larger retailers such as Best Buy ( BBY), Borders ( BGP) and Toys R Us will be targeting the mall zombies this Halloween as part of a larger seasonal push. Toys R Us plans to open 600 Toys R Us Express stores alone this holiday season, snatching up small, vacant retail properties across the U.S. and hiring an extra 45,000 seasonal workers to help run them. With the toy-and-games giant building toward an IPO next year and fending off competition from Wal-Mart ( WMT) and Target ( TGT), Toys R Us hopes the pop-up shops can expand upon the success enjoyed by in-store FAO Schwartz boutique shops last holiday season. "I don't think they would make that kind of commitment and move forward with the number of locations that they have if they didn't think they were going to succeed with that strategy," says Daniel Butler, vice president of retail operations for the National Retail Federation. "Fourth quarter is an important time of year, and I can understand why a lot of businesses would expand their business in that quarter." For seasonal retailers, the short-timer stores are a longtime tradition. This year, for example, independent retailer Spirit Halloween will open 850 shops in empty storefronts across the United States for exactly one month. For major retailers, however, such shops are usually more about testing the waters than tapping into seasonal spending. Before opening its Herald Square location in New York City last year, J.C. Penney used a pop-up store to take the temperature of its potential customer base. Other retailers from small fashion chains to Calvin Klein have used a similar approach. "It can be a great way to boost sales and support your existing locations and your website," Butler says. "It's a way you can test new products and formats on a smaller scale before you make an investment on a large scale, but sometimes you just do it for the seasonal boost, depending on your business strategy."