The company stirred excitement this month by offering a line aimed at girls called the Research Institute, Lego's first offering to feature women in a professional setting rather than at play or partying.
The set included three female scientists in their respective labs (without the pink frilly dresses worn by the girl Legos in the company's best-selling Friends line).
Its introduction made news, especially given the pressure the company faced this year when a little girl's letter went viral - she had begged Lego to produce more realistic sets for girls that gave them adventures and jobs rather than beach get-ups or baking duties.
Within days of its appearance early this month, the Research Institute - a paleontologist, an astronomer and a chemist - sold out on Lego's website and will not be available at major retailers, including Target and Wal-Mart.
Toys R Us did carry the line, but according to associates reached by telephone at two of its New York stores, it sold out at those locations as well.
A Toys R Us spokeswoman, Kathleen Waugh, said in an email that it would be available in about a week at the company's Times Square and F.A.O. Schwarz stores.
Lego said the set was manufactured as a limited edition, meaning it was not mass-produced. The true enthusiast can still buy the Research Institute at Amazon.com, however, but for about three times its $19.99 retail price.
Another sign of the set's popularity is a Twitter feed @LegoAcademics created by Donna Yates, an archaeologist who is a research fellow at the University of Glasgow. She has been posting the figures in humorous scenes of academia - and since her first Twitter post on Aug. 8 has attracted more than 24,000 followers.
Two years ago, Lego introduced its Friends line aimed at girls, a series of kits that has been successful. In 2013, profits at the company, based in Denmark, rose 9 percent to 6.1 billion kroner (about $1 billion).
The Friends figures, set against backdrops like a catwalk, a beach house, a fashion studio and a beauty shop, met with some criticism, and parents clamored for figures with less traditional gender roles. (In addition to the catwalk, Lego Friends now includes a "first aid jungle bike" and a "jungle rescue base" where the figures help their friends.)
The Research Institute was developed by Ellen Kooijman, a geochemist based in Sweden, and submitted through Lego's fan-sourced Ideas platform, where fans can propose their dream Lego landscapes.
Lego can choose to green-light submissions that get 10,000 votes, and typically produces them as limited-edition items, according to Michael McNally, Lego's senior director of brand relations.
The Ideas lines include a DeLorean time machine, based on the car made famous in the "Back to the Future" movies, and the Ecto-1 car featured in the "Ghostbusters" films.
McNally said the company began reviewing the proposal for the Research Institute in January.
"This awesome model is an inspiring set that offers a lot for kids as well as adults," Lego said of the Research Institute on its website in June.
As is typical with Lego's Ideas products, the set received limited distribution and marketing, according to McNally, who declined to say how many units the company produced.
Over the last few years, toy manufacturers have increasingly experimented with products aimed at girls. Hasbro came out with its Nerf Rebelle line of spongy foam dart guns, and Mattel introduced a Barbie construction set through Mega Brands' line of building blocks before announcing in February that it would buy the company outright.
Toy experts say that manufacturers are starting to realize that some traditionally male toys may appeal to girls, too, and vice versa. Bronies, adult male fans of the My Little Pony toy line, regularly hold conventions, most recently gathering in Florida this month.
"I think what we're starting to see a gender breakdown in the toy aisles," said Jim Silver, editor-in-chief of Time to Play Magazine.
Perhaps. Even so, some have been a tad disappointed with the faces and the painted-on shapes of the new research figures. They're all wearing lipstick, and at least one has drawn-in curves.
On her blog, Kooijman praised the final Research Institute line but said she "strongly" discouraged wearing makeup in the lab because of the potential for contamination.
And Kelli McCannell, president of Hardy Girls Healthy Women, a nonprofit group that criticized the Friends line, questioned the dolled-up toys.
"While I think that women should be able to wear any makeup that they want, I think it's funny that had to be included on the girls, and that the girls would find that fun," she said. "I guess it's two steps forward, one step back sort of thing."
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