"Kilroy Was Here" was conceived by lead singer Dennis DeYoung as an album and accompanying stage show, which opened with a short film of the same name. While the supporting tour was a financial disaster, the album sold over 1 million copies and peaked at #3 on the US charts. However, it broke the streak of multi-platinum albums for Styx and ushered in a more keyboard-oriented, progressive rock direction that would divide DeYoung and guitarists James Young and Tommy Shaw, ultimately leading to their acrimonious split in 1984.
The album's somewhat rock-operatic story tells of a future where rock music is outlawed by a fascist government and the "MMM (the Majority for Musical Morality)". The story's protagonist, Kilroy, is a former rock star who has been imprisoned by MMM leader Dr. Righteous. He escapes using a disguise (according to the album's famous song "Mr. Roboto") when he becomes aware that a young musician, Jonathan Chance, is on a mission to bring rock music back.
Despite its success and well known hits, after the replacement of singer Dennis DeYoung in 1999 the current lineup of the band essentially disowned the album and quickly phased its songs out of their live sets with exception of segments from "Mr. Roboto" and "Heavy Metal Poisoning" when they perform the Cyclo-medley. DeYoung still performs songs "Mr. Roboto" and "Don't Let It End" during his solo tours.
Three of the four videos for the album - "Mr. Roboto", "Don't Let It End", and "Heavy Metal Poisoning" - were filmed at the same time and used footage from the minifilm. A fourth video, "Haven't We Been Here Before", was filmed a few months after the album was released; it did not interact with the album's story.