In the original comic, the Sad Sack's name is just that, Private Sad Sack, and he was even given an uncle, a colonel named Saggy Sack. But in the movie, the Sad Sack's name is Meredith Bixby.
Her role as the major in this Jerry Lewis comedy was the final theatrical feature film for Phyllis Kirk. The remaining 13 years of her acting career would be working on television.
Final movie of Phylis Kirk, after that she started working on TV series.