Rebecca Stoné (pronounced "Stone", the accent is silent) (played by Rachel Tietz) is one of the supporting characters for Demo Reel. She is a scatter-brained actress who originally performed one-woman shows before joining Demo Reel. She performs several roles in each Demo Reel film, including ones meant for men or boys. She also works as a security guard for a Chicago warehouse that may or may not be run by the mafia, as implied by a scene where the three Demo Reel characters are looking over scripts in a warehouse and hear the sound of someone being whacked in an adjacent part of the warehouse.
In The Review Must Go On, it is revealed that the Demo Reel world is in fact a purgatory for the Nostalgia Critic character where he must atone for a lifetime of harsh criticisms. It's therefore possible that Rebecca represents the actors and actresses the Critic made fun of in his reviews.