You are making good time in your first marathon when... Batman, the Dark Knight, overtakes you on the way to the finish line.
Or maybe, you are cheering on the sidelines when you spy Wonder Woman blazing past the ranks of competitive runners.
It's a bird, it's a plane... it's an informal fraternity of runners who revel in completing full marathons in Singapore, masked and costumed as superheroes.
Besides Batman and Wonder Woman, there is Catwoman, Captain America, Zorro and Peter Pan - all serious runners with more than 130 marathons among them.
Their goal? To stop gunning for record times and bring more fun to long races.
Mr Francis Chia, 51, who dresses up as Zorro, says marathons became boring for him after he completed several between 2006 and last year.
"I prefer to stop and help people who are in pain along the way because I know it's not easy," says the IT consultant, who is married and has a 14-year-old daughter.
His best marathon time is four hours and 40 minutes.
"I decided to stop going for personal records and dress up instead to lighten the mood of the race and cheer on the runners."
He chose Zorro because he already had a black compression running suit. Being Batman was out as another runner here was already dressing up as the superhero regularly.
"I thought of Zorro because he dresses in black. Although he's not a superhero, he's a common man with special skills and knowledge," he says. "So I thought I would be a common man, running along with others and suffering with them."
Costumed runners have exploded onto the global marathon scene in the last decade, notably the London, Boston, Tokyo and Hong Kong marathons.
Among the first in Singapore was Ms Jenap Said, who dresses up as Catwoman. The quality control manager in a market research firm began running in costume ever since her first marathon in 2006, the Standard Chartered Marathon Singapore.
"At first, I would change costumes for every run," says Ms Jenap, 54, who started running in conventional sports gear in 2002. "I've run as Santa Claus and Betty Boop before. But Catwoman was my first superhero costume and it soon became my signature. Many runners asked me if I felt warm running in the costume but I was okay."