At least two people were originally credited under pseudonyms.
John Jennings, who wrote the book, music and lyrics, originally used his own name only for the music and lyrics. The book was credited to Joseph Benjamin.
In addition, Phil Landi was originally credited with staging the musical numbers, but that was a pseudonym for Ron Field. Several months into the run, he was credited as Ronnie Fields. Perhaps Fields rather than Field was a typo that was eventually adjusted but in the programs we’ve seen, it says Fields.