[5] Another notable stage performance was as the young bride Eleanor in the 1985 production of A. R. Gurney's The Middle Ages at the Whole Theater Company, established by Olympia Dukakis in Montclair, New Jersey.

[8] Rupp's list of stage credits includes appearances in Terrence McNally's Frankie and Johnny in the Clair de Lune and Cynthia Heimel's A Girl's Guide to Chaos, the Broadway role which propelled her career forward.

Directed by Wynn Handman, and sharing the stage with Rita Jenrette, Rupp's performance as Cynthia was immortalized by legendary caricaturist Al Hirschfeld and described in a New York Times review as "an appealing mixture of pluck and pathos".

After returning to the stage, Rupp explained, she was often cast as an ingénue, but after her portrayal of Cynthia in Chaos, she began getting calls to audition in Los Angeles for "really crazy neurotic" parts in television pilots.

She was realistic about the unpredictability of an acting career, and since she had promised her mother she would never wait tables when she left for New York, she had not given up her part-time work as a bookkeeper and was "learning computers" as something to fall back on.

In 1990, Rupp returned to New York City to perform in a Broadway stage production of Cat on a Hot Tin Roof with Kathleen Turner at the Eugene O'Neill Theatre.

[citation needed] In 1995, she began her stint as Jeff Foxworthy's sister-in-law Gayle on The Jeff Foxworthy Show, appeared in the science fiction miniseries The Invaders with Scott Bakula, portrayed Jerry Seinfeld's annoying booking agent Katie on an episode of Seinfeld (a role she reprised in 1996), and performed on stage as Meg in Broken Bones, a dark drama about spousal abuse by Drew McWeeny and Scott Swan, as part of a one-act play festival at Hollywood's Met Theater.

Rupp appeared in several episodes of Friends as Alice Knight, a home economics teacher who fell in love with and married Phoebe Buffay's (Lisa Kudrow) much younger half-brother, Frank Jr. (Giovanni Ribisi).

She also portrayed Marilyn See, wife of astronaut Elliot See, in episode 11 of the Emmy Award-winning television miniseries From the Earth to the Moon, produced by Tom Hanks and directed by Sally Field.

[23][24][25] After That '70s Show ended in 2006, Rupp appeared in a dramatic television role as the wife of a murdered pharmaceutical CEO on the crime drama Law & Order: Special Victims Unit.

[27] The play showcased a sex therapist's life, from fleeing the Nazis in the Kindertransport and joining the Haganah in Jerusalem as a scout and sniper, to her struggles to succeed as a single mother coming to America.