Peggy Cass received acting training at HB Studio[1] in New York City and eventually landed the lead role of Billie Dawn in a traveling production of Born Yesterday.

[3] She played several characters throughout the performance, including: the mother in "The Wolf at the Door", the narrator of "The Little Girl and the Wolf", a nameless American tourist (who insisted Macbeth was a murder mystery), Miss Alma Winege in "File and Forget" (who wanted to ship to Mr. Thurber 36 copies of Grandma Was a Nudist, which he did not order), Mrs. Preble in "Mr. Preble Gets Rid of His Wife", Lou in "Take Her Up Tenderly" (who was helping to make old poetry more cheerful), and Walter Mitty's wife.

The book, written by Auntie Mame author Patrick Dennis, included photographs by Cris Alexander of Cass, Dody Goodman, Kaye Ballard and others who portrayed the novel's characters.

[4] In the late 1960s and early 1970s, Cass succeeded other actresses in Don't Drink the Water (as Marion Hollander) and in Neil Simon's Plaza Suite, and played Mollie Malloy in two revival runs of The Front Page.

[citation needed] On To Tell the Truth and other series, she often displayed near-encyclopedic knowledge of various topics and would occasionally question the logic of some of the "facts" presented on the program.

She also appeared in the late 1970s on Shoot for the Stars hosted by Geoff Edwards, which was another game show that partnered contestants with celebrities, also filmed in New York City.