"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 debuted at #10 on the Billboard 200 in its first week and sold over 1 million copies (though some sources say two and a half 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, Robert Orin Charles Kilroy (DeYoung), is a former rock star who has been imprisoned by MMM leader Dr. Righteous (Young). He escapes using a disguise (according to the album's famous song "Mr. Roboto") when he becomes aware that a young musician, Jonathan Chance (Shaw), is on a mission to bring rock music back.
Despite its success and well-known hits, after the Kilroy Tour, the songs were ignored during all subsequent tours, with the exception of segments from "Mr. Roboto" and "Heavy Metal Poisoning" performed in the 'Cyclo-medley'. DeYoung did perform the 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.