Some online sources incorrectly suggest that the cover with the color photograph of Judy Holliday was used on the first stereo issue in 1958. That first stereo issue used the same photo of Holliday and the same basic design that had been used on the original mono-only issue. The cover with the color photo is from a reissue from 1960 or so.
During the pre-Broadway run, the list of musical numbers in the playbill listed "It's a Perfect Relationship" as being performed by "Ella and Boys." Perhaps because the jackets for cast recordings were often printed before the Broadway opening, the song was listed as being performed by "Judy Holliday, Boys" on the original LP issue and on some subsequent issues, even though the only "boy" whose voice is heard on the track is Sydney Chaplin, who has a couple of spoken lines.
Most — perhaps all — issues of the recording list "Hello, Hello There!" as being performed by "Judy Holliday, Sydney Chaplin, Ensemble," even though the voices of Holliday and Chaplin cannot be discerned and they may not have performed on that track at all at the recording session. Holliday and Chaplin may have been listed because the playbill listed the song as having been performed by "Ella, Jeff and Ensemble."
This was the first Columbia original cast album to be recorded in stereo, but it was not the first Columbia original cast recording to be issued in stereo. The first Columbia cast recording to actually be issued in stereo (at least on LP) seems to have been West Side Story. Although also originally issued only in mono, West Side Story seems to have been first issued in stereo in September 1957, two months before Bells Are Ringing was issued in mono. The first cast recording to have been issued simultaneously in stereo and mono was Goldilocks.
The mono version of the Bells Are Ringing cast recording contains a difference mix on "Just in Time."
The 2001 CD issue contains longer versions of "Hello, Hello There!" and "Mu Cha Cha" than had been issued previously.