pbr Whoopi Goldberg is joining the cast of Sister Act The Musical, the stage show of her 1992 hit film.br ppbr Last year at the launch of the theatre production, which she co-produced, the actress and comedianne ruled out appearing in the show at the London Palladium.br ppbr "No I'm not going to be in anything on stage," the 54-year-old declared.br ppbr However it seems she has had a change of heart and will now join the musical for a three week stint in August.br ppbr Goldberg will not reprise her role as show girl and cabaret star Deloris van Cartier. Instead she will take over from Sheila Hancock as the Mother Superior.