Whether eccentric or insane, courageous or inspirational, for some a gruelling 26.2-mile run is just not enough. Here we round-up some of the more unusual entrants in this year's London Marathon.
LLOYD SCOTT - AKA INDIANA JONES
Lloyd Scott is re-enacting a scene from Raiders of the Lost Ark
Now something of a regular fixture, Lloyd Scott is back and this time he's come as movie legend, Indiana Jones.
The Leukaemia survivor first proved his mettle to a bemused audience in 2002 when he crossed the finishing line more than five days after he set out dressed in a 130lb deep-sea diving suit.
Last year, he faced the challenge on St George's Day, in a suit of armour, complete with model dragon in tow.
And this year, the accomplished fundraiser is hauling an 8ft-wide, 300lb boulder around London, in a re-enactment of a famous scene from Raiders of the Lost Ark.
"No matter how hot it gets, the hat is going to stay on," he told BBC News.
Lloyd, who expects to complete the marathon at 0800 BST on Monday, is raising money for the Unicorn Theatre for Children and First Step charities.
SUSIE HEWER - THE SCARF KNIITTER
Susie Hewer is running with a large ball of wool
She is unlikely to get much use out of it in Sunday's soaring temperatures, but Susie Hewer is hoping to knit a scarf while running the marathon.
The veteran marathon runner, who turns 50 later his year, also wants a place in the record books for the longest scarf to come out of a marathon.
But for the world record, she will have to make sure she doesn't drop a stitch on her 26-mile journey.
"I'm going to be using large-sized needles and wearing a little apron so I can carry my yarn with me," she said.
Susie, from East Sussex, aims to raise £3,000 for the Alzheimer's Research Trust, and is running in memory of her mother Peggy who died two years ago.
ANGUS MACFADYEN - ON CRUTCHES
Angus Macfadyen wants to set a new world record on his crutches
Last year, Angus Macfadyen was at the London Marathon working as a cameraman for the BBC. This year, he is running, or indeed hobbling.
After a serious accident put him on crutches for over four months, the Londoner decided to make it his trademark way to get around - even after a full recovery.
He is hoping his training, which involved travelling 600 miles on crutches, will stand him in good stead to set a new world record for the fastest marathon on crutches.
"It's going to be punishing crossing the line at 5pm," he told BBC News.
Angus hopes to raise £10,000 for the No More Landmines Trust.
DAVID SULLIVAN - THE GOLFER
David Sullivan has played golf from John O'Groats to Lands End
Setting off in an early pack might seem preferable, but David Sullivan was hoping to be last to cross the start line.
With a full set of clubs and a supply of rubber balls, David is planning to combine the marathon with golf and hit balls around the full length of the course.
Although he expects to take longer than most, he is hoping for a time of six-and-a-half hours.
David's fundraising target is £1,000 for the Variety Club Children's Charity.
Speaking to BBC Radio Five Live earlier, David, from Surrey, was in a confident, yet humble, mood.
"It is monotonous. Please don't think I'm trying to make light hearted of this and trying to enjoy the stuff. I enjoy...endurance racing and I'm very fortunate to be here.
"We have a couple of days of hardship, they [the children] have a lifelong hardship in front of them. It [puts] it all in perspective really. It makes it very easy."