When the evil monk utters his spell at the end of the movie, the spell includes the phrase "Klaatu barada nikto", which was the phrase uttered to control Gort the robot in The Day the Earth Stood Still.
Army of Darkness uses "Klaatu barada nikto" (originally from The Day the Earth Stood Still) as the phrase that must be uttered before taking the Necronomicon. In Read or Die the evil monk uses the same phrase in his spell at the end of the movie.