NEW YORK (CNN/Money) - Suddenly it's hip to be square -- White Castle-style.

The offbeat burger chain -- best known for its 10-piece sack of tiny two-and-a half-inch square, steam-grilled and onion-topped burgers -- is attracting a clientele other than just late-night clubbers.

Retailers say White Castle logo T-shirts, hooded sweatshirts, wristbands and even briefs, have taken off with fashionistas and trend-starved teenagers on the hunt for a new fad.

"It started last summer with the logos of old baseball teams," said LaVelle Olexa, senior vice president of fashion merchandising at department store chain Lord & Taylor. "It's part of a whimsical trend in the contemporary market, an attitude that takes inspiration entirely from pop culture."

Marshal Cohen, analyst with NPD Group, agreed with Olexa's views.

"In part, it's the popularity of everything retro, but it also shows the power of culture over fashion," said Cohen. "The fashion inspirations lately are not coming from established designers but from the entertainment industry, from popular culture, music and the movies."

Lord & Taylor this month started selling two versions of the popular White Castle T-shirts priced at $24 each. One features the slogan "Grab a Snack," the other reads "Always Open Always Tasty."

Department store chain Macy's and teen trendsetters Hot Topic and Urban Outfitters also are stocking up on the clothing.

Larry Levine, CEO of Blacklick, Ohio-based T-shirt manufacturer Earthtones Inc., estimates that his company has already sold between $750,000 to $1 million worth of White Castle clothing paraphernalia to retailers since the beginning of the year and that figure could reach several million dollars by the year end.

"We acquired the exclusive license for White Castle last fall, but we never expected the products to take off so well," Levine said.

Besides T-shirts, the company is also slapping on the burger chain's logos on sweatshirts, mugs, trucker hats and underwear.

Levine predicts White Castle could become one of the hottest brands over the next six months. "It could certainly break the top three, along with John Deere and Orange County Chopper logos," he said. John Deere, which is a larger piece of the business for Earthtones, is estimated to hit $20 million in sales by the end of the year.

"We're very flattered by all this attention. By going into Lord & Taylor, we've really gone full circle," joked Jamie Richardson, director of marketing for White Castle.

The privately held chain has been selling burgers since the 1920s, about 30 years before McDonald's began to spread its golden arches to almost every street corner in the country.

"As a company, we've remained focused on being genuine, distinctive and satisfying the customer's craving," he said."We're not about being mainstream like some of our competitors."

That could soon change, said Earthtones' Levine. "White Castle is certainly going mainstream now," he said, especially with its starring role in a New Line Cinema movie out at the end of the month entitled "Harold & Kumar Go to White Castle." (New Line is a unit of Time Warner, which also owns CNN/Money.)

Said White Castle's Richardson. "It's very exciting for us. The comedic leads in the film reflect the face of America today. One is Korean and the other is Indian. It's about two guys who set out at night to find a White Castle and everything that happened to them along the way."

"We're hoping the movie will entice more people to come to White Castle," he added.