A frowning horse plush has become a viral bestseller ahead of Lunar New Year celebrations for the year of the horse in China.

The sad-looking soft toy was originally made in error after a worker sewed a smile on the horse upside down, the owner of Happy Sister – a shop in the eastern city of Yiwu – told Reuters news agency.

Zhang Huoqing had expected to have to issue a refund to the customer who bought the toy, but after an image of it started circulating online the horse began selling out.

Zhang said the animal’s gloomy expression was resonating with young workers in China.

“A lot of customers like it, and they said it makes sense: that it suits the spirit of today’s corporate slaves,” Zhang said.

“This crying horse really fits the reality of modern working people,” she added.

“People joked that the crying horse is how you look at work, while the smiling one is how you look after work.”

Zhang’s factory has surged production to meet demand – including from other countries, according to media reports.

One buyer, known online as Tuan Tuan Mami, was quoted by the South China Morning Post as saying: “This little horse looks so sad and pitiful, just like the way I feel at work.

“With this crying toy in the Year of the Horse, I hope to leave all my grievances at work behind and keep only happiness.”

The newspaper says the horse is about 20cm (7.8in) tall and costs 25 yuan (£2.62). It is red for good luck, with a golden collar and bell around its neck, and has the phrase “money comes quickly” embroidered on its body in golden letters.

Another shop owner in Yiwu, Lou Zhenxian, told Reuters she thought the toy was ugly, but “it’s the kind of emotional value young people look for these days”.

She described young people going to work in the kind of state like the crying horse, and when you get off work “being immediately happy”.

“But actually if everyone chases that kind of sentiment, the young people’s way of thinking, it’s not quite right. I believe you should work hard when at work and be happy after work, it shouldn’t be two extreme opposites,” she said.

Lunar New Year will be celebrated in February to usher in the year of the horse – one of 12 animals repeated in a cycle under the Chinese zodiac calendar.