I was in my teens. One day, on television, an Italian film. The central scene takes place at a movie theater. A cowboy in a Western film points his gun at the theatre and pulls the trigger, killing one of the viewers in the audience.
When examined by the police, the projection screen reveals a small bullet hole.
Each time the film with in the film is played back someone else is shot. The last victim, a policeman who knows the shot is coming and who tries to evade the gunman by running up and down the theatre is followed by the cowboy, who merely adjusts his aim and mercilessly guns the man down. The cowboy then throws his cigar butt through the screen, which — if my memory doesn’t fail me — is later found by the police.
What this cowboy did was breaking the fourth wall. Breaking the fourth wall indicates self-awareness of the medium and can be found in all the arts. The practice is usually designated by the prefix “meta- ” + “art form x.”
I like it a lot.