The Andrews Sisters were brought in after filming wrapped and the final nightclub footage was edited in after the film's completion.
This film went into production under the title "Oh Charlie!" as Bud Abbott and Lou Costello's second feature film and follow-up to their wildly successful Buck Privates (1941). Production was completed in February 1941 just as "Buck Privates" was breaking box office records across the country, and Universal was worried that the new scare comedy had no real connection to the first hit (preview audiences reportedly asked where The Andrews Sisters were). A nervous studio decided to shelve "Oh Charlie!" and rework it at a future date and concentrated instead on pushing a new service comedy, In the Navy (1941), through production as the team's next feature. Upon completion of "In the Navy," this film went back into production in May 1941 as "Hold That Ghost" with the addition of the opening and closing nightclub scenes (which added Mischa Auer, Ted Lewis, The Andrews Sisters and musical numbers to the proceedings). The new scenes required a rewriting and reworking of the existing footage. Joan Davis, who had by that time reported to 20th Century-Fox for a role in Sun Valley Serenade (1941), was unavailable for the re-shoots and had to be written out of the new scenes (including the new nightclub finale).
Joan Davis was not available for all of the retakes, particularly an end gag in the tavern/nightclub. But, because her back is to the camera for one shot at the end of the tavern money counting scenes, it was assumed that this was not Davis but a double. However, according to "Hold That Ghost: The Complete Filmscript," which utilized studio records, Davis was on hand for retakes during that sequence. In the rush to complete the retakes she just happened to be facing the wrong way.
In two street scenes in the Universal Picture Frisco Lil (1942) a theater marquee is seen. "Hold That Ghost" is the movie shown as now playing at the theater.