Jessie J will pull off a hair-erasing feat as she shaves her head on live TV on Friday night, while many of the biggest names in comedy do their bit for Comic Relief.
Miranda Hart, Dawn French, James Corden, David Walliams and Hollywood star Will Ferrell will appear in sketches or in person during the evening in the traditional Red Nose Day broadcast on BBC One and BBC Two.
Price Tag singer Jessie - also a panellist on The Voice - will be enduring one of the biggest sacrifices as she is parted from her glossy black bob during the programme to boost the millions of pounds being raised.
Red Nose Day celebrates its 25th anniversary this year with presenters for tonight's show including Rob Brydon, John Bishop, Davina McCall, Nick Grimshaw, Jonathan Ross and Russell Brand.
During the evening, Miranda will round off her week of live TV challenges, Miranda's Mad March, in addition to starring in a special edition of Call The Midwife, alongside Jessica Raine, Pam Ferris and Jenny Agutter.
Popular sitcom The Vicar Of Dibley will return to TV for the first time in seven years with a one-off sketch, created by Comic Relief boss Richard Curtis.
James Corden will be reviving his role as Smithy from Gavin And Stacey and Will Ferrell is to return to his character Ron Burgundy from hit movie Anchorman.
Even X Factor chief Simon Cowell will be showing his lighter side by taking part in a spoof in which he is seen to walk down the aisle in a wedding sketch, alongside David Walliams dressed as a blushing bride.
Other highlights of the evening will include the return of David Brent as Ricky Gervais for a brief revival of The Office, in which he shows off his new career as a wannabe music mogul, Rowan Atkinson will address the nation as the new Archbishop of Canterbury, sharing his views on the importance of fundraising for "Red Nose in Need" and Peter Kay will be seen undertaking his challenge to spend much of the week perched on a sofa, as well as unveiling his new video for the James hit Sit Down.
In addition, there will be hundreds of smaller events around the country encouraging people to give to projects in the UK and Africa, including a special nationwide Bake Off challenge.