It was when she got a midnight phone call from the police that Mrs Jayne Kwek knew her advertising campaign had really taken off.

It was 2005, and the chief executive of ComfortDelGro's advertising arm Moove Media had just launched the first of a series of teaser campaigns by putting 2D wooden cut-outs of cows in open spaces around the island.

Mrs Kwek, 61, recalled how that night she listened, baffled, as the policeman on the line told her that three youngsters were trying to steal one of her cows, and asked if she wanted to have them arrested.

Mrs Kwek declined to have the perpetrators of this bizarre form of flattery detained. She said: "I didn't want anything negative to come out of it, and they must have liked the cows enough to want to do this.

"I mean, these cows are not easy to yank out. And they were huge enough that they couldn't go into a car boot, these people had to use a van to steal them," she said.

The determination of the thieves, as well as the policeman who pleaded with her to "let him save (her) cows", gave Mrs Kwek her first clue that the cows had captured the public's imagination.

That year, Moove lost almost 40 per cent of its cows. The next year, it put out to pasture a range of flower-themed cows which Mrs Kwek still considers her personal favourites. Six in 10 vanished.

Nine campaigns and more than 4,000 cows later, Moove no longer loses so many cut-outs - thanks largely to a strategy of positioning them under CCTV cameras - but has continued to trot out new themed cows year after year, from polka dot cows to cows in vocational outfits.

This year's campaign marked SG50 with eight cows based on historical characters such as samsui women, Peranakan Nonyas and wayang opera singers, plus a soldier cow. The last, which was specially requested for the National Day Parade period, is a parachuting cow in vintage army fatigues, suspended from lamp posts.

Although she has a creative team who flesh out the designs for each year's campaign, Mrs Kwek - an advertising veteran with a fashion merchandising degree from Daytona Beach Community College in Florida - gets the first and final word on how the cows turn out.

The cows often take shape from doodles she makes at all times of the day on whatever is at hand - whether scraps of paper or napkins.

The final design must also meet her exacting standards before going out to the masses. "If there is one stroke out of place, I throw it out," she said.

She considers the cow her spirit animal. "They are peace-loving, focused and nurturing, and we benefit from all parts of them," she said.

So when she needed to come up with a transport advertising campaign, she decided to milk the pun of "moo" and "move" for all it was worth. "I expected to turn these cows into cash cows, and I did," she quipped.

A Moove spokesman said the advertising revenue it has raked in for ComfortDelGro has grown by close to 100 per cent since the brand's inception in 2005.

Regarding her bold move not to put a name to what the cows were advertising, Mrs Kwek said: "You don't have to scream to be known. That would have killed the whole campaign. I kept people talking and it was more lasting that way."

Besides the Moove cows, she is also responsible for other campaigns such as the SG50 Red Dots, red foam balls which could be clipped to car windows. The sale of 50,000 "red dots" raised about $250,000 for charities such as the Lion Befrienders Service Association.

One might say that outdoor advertising runs in Mrs Kwek's blood. Her mother Laura Tan founded 3 Aces and built it into Singapore's largest outdoor bus banner agency. Mrs Kwek grew up seeing the streets full of her mother's ads for big-name clients such as Exxon and Knife Oil.

Mrs Kwek said that she draws inspiration from the work ethic of her 87-year-old mother, who still goes to the office once or twice a week. "She is a fireball. We caught her energy at home from an early age."

Mrs Kwek ran her own ad agency CityDreams for a few years, after a stint with her mother's company. After she sold CityDreams and took a brief hiatus, she joined ComfortDelGro in 2004.

Married to a former air force colonel, the mother of three sons said of her work: "It's never been a chore. It's always been an 'aha' moment.

"Singapore is a playground that I can make magical and whimsical, and bring smiles to the people here."