The "WHO IS R?" campaign was a unique marketing campaign in Bulgaria for the LG KC910 Renoir mobile phone. It involved creating an imaginary persona named "R", portrayed by an actor who interacted with people in the city over 10 days without revealing the purpose. The campaign gained popularity for the phone and brand through mystery "teasing" and "reveal" phases using guerrilla marketing tactics like distributing ice hearts and posters around the city, as well as maintaining an online presence through blogs and social media. This unconventional approach generated buzz and intrigue.