Ellie Goulding, Gareth Bale and Chris Froome are just some of the big celebrity and sporting names taking on the 2.6 Challenge this weekend.
It's been put together by organisers of some the UK's biggest mass participation sports events - including the London Marathon - and it's all for a good cause.
The 2.6 Challenge is aiming to help charities that are struggling right now, with many fundraising events being cancelled during the coronavirus pandemic.
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When is it?
The 2.6 Challenge officially begins on Sunday 26 April, on what should have been the 40th edition of the London Marathon.
Where is it taking place?
The 2.6 Challenge is happening all over the UK, and is open to anyone of any age.
The only rule is that the activity must follow the Government guidelines on exercise and social distancing.
What do you have to do?
The idea is that people choose a challenge, any challenge at all, related to the numbers 2.6 or 26 (the number of miles in a marathon, plus the date the event would have taken place).
"You can run or walk 2.6 miles, 2.6 km or for 26 minutes. You could do the same in your home or garden, go up and down the stairs 26 times, juggle for 2.6 minutes, do a 26 minute exercise class or get 26 people on a video call and do a 26 minute workout - anything you like," says Nick Rusling, one of the event organisers.
You can either donate to other people's challenges, or make up your own activity and fundraise for it. This will hopefully make up some of the money lost through the London Marathon not going ahead.
What are other people doing?
Nine-year-old Melissa has chosen to sit in a bathtub of cornflakes for 2.6 hours on Sunday to support her mum who works as a nurse in Scunthorpe.
Real Madrid and Wales international footballer Gareth Bale will be attempting 26 keepie-uppies, followed by a bicycle kick volley for his 2.6 Challenge.
And 13-year-old Welsh table tennis star Anna Hursey is taking on a table tennis challenge to hit the most targets in 26 seconds to raise money for the NHS.