Billy the Puppet

Billy is a puppet that has appeared in the "Saw" franchise. It was used by John Kramer to talk with his test subjects by delivering recorded messages, often appearing on a television screen or occasionally in person to describe the details of the traps and the means by which the test subjects could survive.
Although it has never actually been identified in the movies, "Billy" is the name by which it is referred to by writers, directors, and members of the cast and crew on documentaries and interviews. The name was given to it by its real-life creator James Wan, who is the director and co-writer of "Saw".