Corrected entry: During the beginning, Tony Curtis and Jack Lemmon are told that in order to be part of the all-girl band they have to be blonde. When they finally dress in drag, Jack Lemmon is wearing a light colored wig, (actually red) and Tony Curtis is wearing a brown wig, yet they are both let in the band.
Corrected entry: In the scenes where we alternately see Curtis with Monroe on the yacht and Lemmon with Brown dancing rhumba, a swish-pan (fast horizontal panning) is used to link the two situations with the cut in the middle. During these you can clearly see light and stage equipment.
Correction: The band leaders were probably so desperate, that they didn't care who they got. Besides, if hair color really mattered, the band leaders would have told Tony Curtis and Jack Lemmon to dye their hair blonde.