Devizes actress and former RAF helicopter pilot Elaine Caulfield is one of five women picked by Activia to star in its new television commercial that went on air on Tuesday.
Chosen from 120 hopefuls, mum Ms Caulfield, 45, appears alongside TV presenter Gok Wan.
The new campaign is designed, say the promoters, to encourage women in the UK to pledge to “feel good from within” in 2013.
Ms Caulfield said: “My friend Karen received an email from Activia saying they were looking to cast real Activia fans to be in their new campaign.
“Karen knew that I also love their yogurts, so we both applied to see if we would make the casting session.
“We were thrilled to find out we’d made it through to the actual shoot.
“The Activia team didn’t let us know who we were starring alongside, so we all got the shock of our lives when Gok surprised us.”
Ms Caulfield has appeared in productions at the Wharf Theatre, including Billy Liar.