It was a joke from a show called "The Critic", about Jay Sherman. A film critic. In one episode it was mentioned that he had once published a book, and book stores had promoted it with these cardboard cutouts that depicted him repeatedly saying "Buy my book!"... said cutouts were quickly removed from stores, cause it's been said that they led people to commit acts of violence, due to how annoying they were:
https://www.youtube.com/watch?v=aDTwO0TlwOU

https://www.youtube.com/watch?v=wyZ7oSnHnio