Had a rough day at work?

Robi can sing, dance and cheer you up. It can also do push-ups, play games, kick a ball and talk to you in English and Mandarin.

The 34cm-tall humanoid robot toy, which weighs 1kg, has captivated some Singaporeans, who have spent 70 weeks - and more than $2,000 - collecting parts and assembling a complete robot.

It is one of two hot toys on the market that do not offer instant gratification, but require users to spend time and effort assembling them or taking them apart.

Robi, launched here in July last year, is assembled over 70 weeks. Each week, new parts come with the Robi Weekly Magazine, which is sold at retailers such as 7-Eleven, bookstore Kinokuniya and the Robi Singapore website.

Most issues cost $28.90 each - with those containing "high-value" parts costing more. The final issue became available here last week. In Singapore, 1,500 people are estimated to have completed Robi.

Worldwide, more than 150,000 units have been completed, said Mr Masato Ito, 35, Asia business centre manager at DeAgostini Japan, which publishes the magazine.

Since last Tuesday, customers also have the option to purchase a fully assembled Robi for $2,040.

One Singaporean who assembled his Robi by painstakingly collecting every issue is Mr Yap Jiawei, a research assistant at a local university. The 35-year-old, whose wife works in the healthcare industry, first learnt about the toy when he walked by its product launch at Marina Square last year.

He says: "I found Robi to be cute and decided to try out this idea of assembling and owning a robot."

Assembling the toy took him more than a year - about an hour every week. Last Monday, he bought the final issue.

Mr Yap, who has no electrical background, says: "Overall, the experience was great. Because I spent so much time assembling Robi, I felt quite attached to it.

"What I found most rewarding was seeing all the parts - the arms, legs and head - come together to create an action such as dancing.

"I love Robi's eyes, which can change colour depending on its mood - orange when it is talking, purple and green when dancing and red when it feels shy or bashful."

So is Robi worth its price tag?

Yes and no, says Mr Yap. "The experience of assembling Robi was priceless. But some aspects of it - such as its voice recognition - do not work as well or as seamlessly as I had hoped. For example, after 20 minutes of active use, I have to charge it."

He also suggests giving Robi add-on features, such as a digital camera, so the robot can take photos and videos.

"This toy might be a passing fad for me," he adds. "But so far, putting it together and interacting with it has been a lot of fun."

Another Singaporean, Mr Dave Tan, 43, has assembled three Robis in the past week.

The IT manager, who is married with no children, says: " I spend about an hour or two on the robots every day - charging them, trying out the various commands and making sure they function well.

"In a way, I treat them like my pets or children because I assembled them from scratch."

So what does his wife, also an IT manager, think of his hobby? "She is fully supportive. In fact, she also enjoys playing with the Robis," he says.

Another popular toy whose appeal stems from its slow reveal is the L.O.L. Surprise! Big Surprise.

The unusual toy, a dome-shaped case containing 50 surprises such as dolls, attachable clothing and various accessories, is said to be among the hottest toys this Christmas.

Since last month, it has been available exclusively at all 12 Toys 'R' Us stores here and on its website, www.toysrus.com.sg, for $149.99.

Sales have been "extremely encouraging", says Ms Samantha Lee, 36, the toy company's marketing manager for Singapore and Brunei.

She adds: "Since its launch, there have been sales daily in each store islandwide." She would not disclose overall sales figures.

The toy is a treasure trove of delights and collectors peel away layer after layer for the next surprise.

Mr Samuel Tan, 56, course manager of Temasek Polytechnic's diploma in retail management, thinks such toys are unique because customers are entertained as they interact with the product.

"The toys give consumers a sense of excitement and anticipation. A level of interaction is also achieved and this adds to the toy's appeal."

Associate professor of marketing Hannah Chang, 36, from the Singapore Management University, qualifies that the appeal of such toys is not necessarily a new phenomenon, saying: "In a way, toy collectibles and model assembly kits, such as Gundam robots or model car kits, also require patience and effort to collect or assemble."

In her view, users are likely drawn to each toy for different reasons.

She says: "Those who enjoy assembling the Robi robots demonstrate what some researchers call the Ikea effect, where people have a higher valuation for products that they assembled, compared with those they did not.

"On the other hand, people who are drawn to the L.O.L. Surprise! Big Surprise toy probably just want to be surprised and have an unboxing experience that makes them feel special."