In The Shining, when Jack Torrance has clearly gone mad and is chopping down the bathroom door with an axe to get to his wife, why does Jack Nicholson say "Here's Johnny!" when his character's name is Jack? Is it completely random and showing how he's gone so insane he's just saying random names, or does it have some sort of significance?
That line was ad-libbed by Jack Nicholson as an imitation of Ed McMahon's intro for The Tonight Show.
Jack Nicholson ad-libbed the line "Here's Johnny!" in imitation of announcer Ed McMahon's famous introduction of Johnny Carson on U.S. network NBC-TV's long-running late night television program The Tonight Show Starring Johnny Carson. Stanley Kubrick, who had been living in England since before Carson took over "The Tonight Show," had no clue what "Here's Johnny!" meant. Carson once used the clip of Nicholson as the introduction to one of his annual anniversary specials.