After the Ghostbusters mistakenly hired a ghost bride named Dixie and got rid of her, Mrs. Spengler was brought on as a temporary secretary until Janine came back from her vacation. Before they could leave for a case, she gave everyone sweaters and handed Ray a thermos containing soup.
She later returned to help Egon with his cold. Mrs. Spengler blended the Spengler Family Remedy, a concoction of chicken soup, orange juice, tea, prune juice, and a dash of garlic for flavor, for her ailing son. Despite her wishes, she and Egon went to Ghost World to investigate. She ends up helping the Ghostbusters bust Karro Zans. She wields a Trap and Ecto-1's spotlights fairly well. Soon after, she decided to stay longer at the Firehouse to take care of Peter, Ray, Winston, and Slimer, who caught Egon's virus.
Mrs. Spengler is a very motherly person, as she also treats the other Ghostbusters like her children as well. Janine and her seem to get along pretty good as well. She had a comically shrill voice and was very supportive but a bit overzealous in her concern for the boys, to the point of asking if they were all wearing clean underwear.
In her second appearance, she is more phlegmatic, like her son. She also exemplified elements of a stereotypical Jewish mother by uttering phrases like "My son, the comedian."
- In the novelization of the first movie, she apparently has another son but he isn't named (though she herself is not mentioned). In it, Egon is said to have commandeered pieces of his brother's train set to use in an experiment when he was young.
- The first acknowledgement of her existence on the animated series was in the third season episode "Baby Spookums" where an embarrassed Egon admits his mother called him "Spookums" as a child.
- Egon's mother apparently shares many physical traits with her son. Most notably blonde hair, similar eye color and the need to wear glasses. In a curious coincidence, Egon's two known ancestors on his father's side also look identical to Egon.
- The second person to voice the role of Mrs. Spengler was legendary comic actress Rose Marie. Best known for her role on the "Dick Van Dyke Show" amongst many other comic roles.
- At Ghost World, she mentions that she took a Karate lesson.
- Egon confided in Peter that Mrs. Spengler threw out his picture of Socrates when he was five years old.
- Her name was never given in any official media, However fans have commonly called her "Katherine Spengler". The name was brought into use by fan fic writer Shiela Paulson. Since then, the name has been used in other fan fics including Fritz Baugh well known "Ghostbusters: Forever". Fritz added the maiden name "Melton".
- On page one of Ghostbusters Volume 2 Issue #1, Mrs. Spengler is referenced on a Post-It note on Janine's computer.
- Marsha Goodman (1989). Episode Call Sheet and SAG Report - "Til Death Do Us Part" (1989).
- Eatock, James and Mangels, Andy (2009). The Real Ghostbusters Complete Collection Booklet, p. 38. CPT Holdings, Inc. Line reads: "Egon's mother makes her second appearance in the series, voiced by Rose Marie (from The Dick Van Dyke Show)."
- Marsha Goodman (1990). Episode Call Sheet and SAG Report - "Ghostworld" (1990).
- Peter Venkman (2009). The Real Ghostbusters - "Til Death Do Us Part" (1989) (DVD ts. 25:00-25:01). Time Life Entertainment. Peter says: "Thank you, Mrs. Spengler."
- Egon Spengler (2009). The Real Ghostbusters - "Ghostworld" (1990) (DVD ts. 14:52-14:57). Time Life Entertainment. Egon says: "Mother, either you leave or I won't call you for the next six months."
- Egon Spengler (2009).The Real Ghostbusters- "Baby Spookums" (1987) (DVD ts. 08:32-08:34). Time Life Entertainment. Egon says: "My mother used to call me Spookums."
- Mrs. Spengler (2009). The Real Ghostbusters - "Ghostworld" (1990) (DVD ts. 15:47-15:51). Time Life Entertainment. Oh boy, this is going to be more fun than my karate lesson!"
- Peter Venkman (2009). The Real Ghostbusters - "The Slob" (1990) (DVD ts. 18:53-18:57). Time Life Entertainment. Peter says: "Egon, you're too late. We had to blast that picture of Einstein your mother threw away when you were 12."
- Egon Spengler (2009). The Real Ghostbusters - "The Slob" (1990) (DVD ts. 18:58-19:00). Time Life Entertainment. Egon says: "I was 5 and it was Socrates."