In modern pantomime, comedy, audience interaction (HE'S BEHIND YOU!! etc), (cross dressing XD), umm, well, it's normally a well known story or fable, eg, Snow White/Cinderella, etc, but in Commedia Del Arté, the origin of pantomime in northern Italy, as well as comedy, and sometimes possibly audience interaction, there would be set characters, such as the Lovers, who were very dramatic and 'mood swingy' and also such as the doctor, who was very silly, comedic and pretended he knew a lot; he was also normally quite fat. There would be masks, set ones for different characters, and these were only put on backstage or facing away from the audience as the audience were made to believe these were the actor's real faces, even though they were usually dark red leather.
Hope I helped!