Nick is currently attempting to cycle 1000 miles on an exercise bike outside the BBC Broadcasting House in London, but he’s not doing it alone and has roped in plenty of A-list pals to get their cycling shorts on and join him.
McBusted have already popped by - minus Tom Fletcher who became a Dad last week - and there will be loads more surprise guests as the day goes on.
Luckily for Nick, all of the miles cycled by his celeb guests, including Daisy Lowe and Professor Green, will count towards his total.
The DJ is completing his cycling marathon as part of the Radio Around The World charity event, which sees all of BBC Radio’s stars attempt to run, swim and cycle the full length of the Earth’s circumference - a staggering 25,000 miles.
The breakfast show host got some professional advice from Olympic champion Victoria Pendleton before starting out and Davina McCall - who recently completed her own grueling Sport Relief challenge - has also popped by to show her support.
Nick is expected to complete the challenge during Greg James's Radio 1 show, which starts at 4pm.