Created by Delaney Lund Knox Warren & Partners and directed by Ben Gregor, the ad shows men going about their daily lives each wearing a pair of giant 'comedy' testicles.
As well as a group doing tai chi, a gardener strimming foliage and office workers in a lift, O'Leary, a patron of the charity, is seen presenting a TV show while wearing the same giant balls. The ad ends with the line "Make your balls a bigger part of your life".
Greg Delaney, DLKW chairman, said: "This is a serious subject which deserves greater attention. We've
deliberately treated it with some humour in the hope that young men will not only enjoy it and take its message on board, but forward it to their mates, so that testicular cancer, which is curable, gets tackled head on."
The ad is a first for Everyman, with previous campaigns having talked about testicular cancer but never actually shown testicles.
Alison Morgan, Everyman's communications manager, said: "We realise that showing men with giant testicles is quite controversial, but the advert has been filmed in such a humorous way that we feel it will appeal to young men, which helps us to spread important messages to them."
Testicular cancer is the most common cancer to affect men aged 15 to 45 years old, with 2,000 new cases diagnosed every year. If caught early the cancer has a 99% cure rate so the importance of regular checking can be life-saving.
Morgan said: "Everyone who has worked on this ad has given their time completely free to help Everyman, a commitment which we appreciate enormously."
"Thanks to them, we hope many more young men will check themselves regularly for the symptoms of testicular cancer, which will ultimately save lives."
The advertisement will be promoted through a viral email linking to a website, noticeyournuts.com, created by DLKW's integrated division, Dialogue DLKW.
The charity's previous campaigns have featured other famous stars, including Robbie Williams, in 1999, and Rachel Stevens, who starred in last years "Rachel gets fruity" viral ad, also created by DLKW, where a scantily clad Stevens told male viewers to put their hands down their trousers and get hold of their testicles.
If you have an opinion on this or any other issue raised on Brand Republic, join the debate in the Forum.