The first scene Clint Eastwood shot was his former director Don Siegel's cameo as Murph the bartender. As a joke, Eastwood made Siegel do 11 takes - then told the cameraman to put the film in the camera.
In one of the film's early scenes, Al Monte is heard telling his listeners that the Monterey Jazz Festival is four months away. Based on the events that unfold, that would mean that the film covers a time span of slightly over four months.
A 1996 documentary called "I'm Your Number One Fan", which was about celebrity stalkers, had a segment which was similar to the plot of this film; A woman called Blue Tulip Rose Read who was obsessed with DJ MIke Read. She even claimed to be married to him and even dressed like him. The documentary shows Blue Tulip Rose Read going to the radio station where Mike worked at, hoping to meet him and also get him to marry her. But security stops her and throws her out.