Arthur Freed bought the rights to the Broadway musical "Very Warm For May", music by Jerome Kern and book and lyrics by Oscar Hammerstein II, as the starting point for the film, originally meant as a vehicle for Judy Garland. In typical Hollywood manner, by the time they were done all the original songs except "All the Things You Are" had been dropped, replaced by material from other writers and the project had been handed over to Jack Cummings. Three of the original songs were sung, fragmentarily, by George Murphy sitting at a piano waiting for Ginny Simms to come out. The name of the original play is also mentioned in passing in one of the scenes.
The original project was intended to be the fifth film in the "Broadway Melody" series, and was to star Gene Kelly, Eleanor Powell, and Lena Horne. Studio chief Louis B. Mayer decided instead to turn it into a vehicle to make a star out of his then mistress Ginny Simms. Horne was then placed into this film in a supporting role and her "Brazilian Boogie" and "Somebody Loves Me" numbers (originally filmed for 'Broadway Melody of 1943') was inserted into this one. Her other number filmed for 'Broadway Melody', "Honeysuckle Rose", was placed into Thousands Cheer along with two other numbers meant for the abandoned film: Eleanor Powell's "Boogie Woogie" tap dance and Gene Kelly with the Flying Corbinos.
The song "What Do You Think I Am?" was originally from the musical, Best Foot Forward, and was cut from the film version.