Her father was a traveling lighting salesman; her mother was born (and raised) in Dalmeny, Saskatchewan, before becoming a teacher and later training as a nurse.

But after her arrival her first and middle names were derived from tennis players Valerie Scott and Kay Stammers who were victorious doubles partners at a tournament Harper's father was attending the day she was born.

[10] Harper based her character Rhoda Morgenstern on her Italian-American stepmother and Penny Ann Green (née Joanna Greenberg), with whom she danced in the Broadway musical Wildcat.

She broke into television on a 1963 episode of the soap opera The Doctors ("Zip Guns Can Kill"), and was an extra in Love with the Proper Stranger (1963).

She was in the ensemble cast of Paul Sills' Story Theatre and toured with Second City along with then-husband Richard Schaal, Linda Lavin, and others, later appearing in sketches on Playboy After Dark in 1969.

She performed several characters in a comedy LP record, When You're in Love the Whole World is Jewish (1965), which included the popular novelty single, The Ballad of Irving, a recitation by TV announcer Frank Gallop.

[16][17][18] While doing theater in Los Angeles in 1970, Harper was spotted by casting agent Ethel Winant, who called her in to audition for the role of Rhoda Morgenstern on The Mary Tyler Moore Show.

[citation needed] She had a starring role in the suspense movie Night Terror (1977), playing a murder witness who's pursued by the killer.

She also starred as Maggie in a telefilm production of the Michael Cristofer play The Shadow Box (1980), directed by Paul Newman.

[21] Harper appeared in various television films, including guest roles on such series as Touched by an Angel (1996), Melrose Place (1998) ,Sex and the City (1999), and That 70's Show (2001).

She played Tallulah Bankhead in the world-premiere production of Matthew Lombardo's Looped at the Pasadena Playhouse from June 27 to August 3, 2008.

[32] It then briefly ran on Broadway at the Lyceum Theatre, from February 2010 (previews) through April 2010, for which Harper received a Tony Award nomination.

[35] On September 4, 2013, Harper was announced as a contestant for the 17th season of Dancing with the Stars, partnered with professional dancer Tristan MacManus.

Harper appeared as the character Wanda on the American comedy web television series Liza on Demand, in its July 11, 2018, episode: "Valentine's Day".

In December, 2024, magician and mentalist Oz Pearlman appeared on the Howard Stern Show and guessed that the word was "curly.

[49] She announced on March 6, 2013, that tests from a January hospital stay revealed she had leptomeningeal carcinomatosis, a rare condition where cancer cells spread into the meninges, the membranes surrounding the brain.

[56] In 2016, Harper's cancer treatment continued at Cedars-Sinai Medical Center, and she was well enough to appear in a short film, My Mom and the Girl, based on the experiences of director/writer Susie Singer Carter, whose mother has Alzheimer's disease.

[59] By July 2019, she was on a regimen of "a multitude of medications and chemotherapy drugs" and was experiencing "extreme physical and painful challenges" that required "around-the-clock, 24/7 care.