Their involvement was revealed as it emerged that the first week of crowdfunding efforts by venues, festival workers and companies across the Fringe had raised more than £140,000 in just over a week.
More than 3000 supporters have contributed to 57 different crowdfunding projects being staged under the banner of “FringeMakers."
The project includes a weekly virtual variety show, which gets underway at 9pm every Friday in August, runs for 90 minutes and cost £9 per ticket.
Venues and performers are able to keep 100 per cent of the proceeds from tickets they sell for the “Fringe on Friday” event.
Underbelly has revealed that a signed photo of Redmayne in the cast of its 2001 show Cabaret, where he played the master of ceremonies in the Cowgate venue, and a signed poster of Peters' hit production Five Guys Named Moe, which Underbelly staged at the McEwan Hall, are among new rewards on offer in return for donations.
Comics Johnny Vegas, Mark Thomas, Romesh Ranganathan and Abandoman, playwrights Kieran Hurley and Gary McNair, Britain’s Got Talent star Lose Voice Guy and magician Gareth White are also now involved in supporting the FringeMakers project, which is aimed at helping acts and venues.
Fleabag creator Phoebe Waller-Bridge, comics Ricky Gervais, Jason Byrne, Daniel Sloss and Craig Hill, and Harry Potter actress Miriam Margolyes have all been featuring in fundraising efforts so far.
Summerhall, Gilded Balloon, Assembly, Pleasance, Underbelly, Monkey Barrel, Zoo, the Pianodrome and the Queen’s Hall are among the venues and promoters fundraising to help support acts who would have performed this year and ensure they can return with full programmes in 2021.
Other acts staging their own fundraising efforts include comics Craig Hill, David O’Doherty and Deborah Frances-White, cabaret star Laurie Black, magician Ava Beaux and children’s entertainers Dr Bubble and Milkshake.
Fringe Society chief executive Shona McCarthy said: “We’ve been genuinely humbled by the generosity of Fringe fans over the past week or so, particularly in times of real financial difficulty for many people.
“Thousands of the artists, venues and creatives that make the Fringe happen each and every year are facing an uncertain future, unsure of where their next performance or paycheck is coming from.
"FringeMakers is designed to tackle this head on, raising vital funds for artist and venue projects large and small.
"Our weekly AJ Bell Fringe on Friday live shows offer another way for Fringe fans to support, with every penny of the £9 ticket price going to Fringe artists and venues."
Underbelly directors Ed Bartlam and Charlie Wood said: “We’re so delighted that more stars of Underbelly’s history at the Fringe have signed up to support artists whose shows have been cancelled this year. We’re hugely grateful to all of them for supporting our fundraising drive for these artists.
“Edinburgh is where it all started, in a dingy cave, 20 years ago. It's our life blood, our home, a place where genuinely anything can happen and incredible memories have been made.
“To not be there this year is heart-breakingly devastating but it is also a time for reflection and understanding that we must step back and put the safety of others first."