Christopher Guest revealed the initial inspiration for This is Spinal Tap at the A.V. Club comedy festival. Rob Reiner's This is Spinal Tap is the legendary mockumentary on the fictional hard rock band Spinal Tap that has spawned countless imitators and has even been turned into a descriptive term to poke fun at musicians and the entire music business as a whole. Many bands have spoken up to claim that they were the inspiration for This is Spinal Tap and there have been a few confirmed stories that made it into the movie, but the original inspiration for the cult-favorite mockumentary has never been revealed.

After taking part in the School of Film live event for A.V. Club's comedy festival, Guest took questions from the audience. One audience member stood up and asked Guest if any of the characters that he has portrayed over the yeas were autobiographical. After making a joke, Guest said that none of his characters over the yeas have been autobiographical, but rather all from his personal inspiration.

Guest then brought up This is Spinal Tap and told the real-life story that inspired This is Spinal Tap. Christopher Guest sets up the story by saying that he was at a hotel lobby in Los Angeles in 1974, waiting for a friend when he overheard a conversation at the front desk. Guest goes on to explain.

"An English band was checking in, this was 1974. The manager and I think there were four of them, they went up to the desk and he started to the thing, I was just waiting for my friend. And the manager says to one of them "where's your bass?" "what?" "Where's your bass?" "I dunno, I think I left it at the airport"

Guest says that the exchange went on for about 15 minutes and that it was the best moment of his life next to meeting his wife. Guest does not reveal who the band was, but he does a hilarious impression of the exchange between the manager of the band and the bass player. It is pretty cool, after all of these years, to hear the real story that sparked the fictional Spinal Tap.

This is Spinal Tap director Rob Reiner has said that a lot of the mockumentary was based off of concert films of the day like the Rolling Stones' Gimme Shelter and the Bands' Last Waltz with a sprinkle of Led Zeppelin's The Song Remains the Same. Many bands have come forward to accuse the fictional band of ripping them off. For instance, Black Sabbath claims that the Stonehenge bit was based off of their actual stage prop, but the movie was filmed a whole year before Sabbath's tour that featured a Stonehenge prop. The British heavy metal band Saxon claims to be the biggest influence because Tap bass player, Harry Shearer did indeed tour with Saxon before the making of the movie.

This is Spinal Tap was carved out of hours and hours of completely adlibbed material by Guest and fellow band mates, Shearer and Michael McKean. All three of the actors wrote the songs and played all of the instruments in the studio and have even played live concerts as Spinal Tap over the years, mostly for charity. Many bands may claim to be the real inspiration for This is Spinal Tap, but they're all wrong as Guest points out. Watch the hilarious video below.