HONG KONG (Reuters Breakingviews) - Pop Mart’s mystery toy boxes may leave shoppers and investors alike with a surprise. The retailer’s shares doubled on their Hong Kong debut, giving it a market capitalisation of nearly $14 billion as of Friday morning. Sales are soaring in its home market, where young adults make purchases without knowing what they will get. But a premium valuation to peers like Hasbro looks equally faddish. Started in 2010, Beijing-based Pop Mart sells figurines and other items targeting young adults. Its most popular toy, a character called Molly described by the company as a “cute little girl with distinctive pouting lips and big lake-blue eyes”, has helped build up a cult-like following among loyal collectors: registered members topped 3.6 million as of June, from less than a million two years ago. The biggest draw, though, may be Pop Mart’s so-called mystery blind boxes, that have boosted recurring sales. Last year, over half of its registered members bought products from the company at least twice. Friday’s triple-digit percentage pop reflects the frenzy around this trend boss Wang Ning has cultivated. Even before, the company raised $676 million at a valuation of over 38 times expected 2021 earnings, according to Refinitiv publication IFR. That’s well above other toymakers like Hasbro and London’s Games Workshop, who trade on 20 times and 29 times respectively. That looks hard to justify. Unlike Power Rangers or Barbie, Molly and other of Pop Mart’s beloved characters are virtually unheard of outside of China, where international sales account for just under 3% of the company’s total revenue of 818 million yuan ($125 million) in the six months ended June. And at home, the company caters to a niche audience. Earnings growth has been uneven too. Net profit jumped by more than 60-fold in 2018, but rose 24% year-on-year in the six months to June. Pop Mart’s biggest challenge will be keeping up the fad. It plans to launch over a hundred new toys next year, and has tied up with Disney and other partners to sell Mickey Mouse merchandise and other action figures. Even so, once the hype fades, investors may not like what they get.